Image display element

ABSTRACT

In a micro light emitting element, a first metal film electrically connected to a second conductive layer is disposed on a surface on an opposite side of a light emitting surface side. The first metal film covers the second conductive layer. A first inclined angle of a first conductive layer side surface from a slope formed around a light emission layer to the light emitting surface is larger than a second inclined angle of the slope. The slope and the first conductive layer side surface are covered together by a second metal film. A first transparent insulating film is disposed between the slope and the second metal film.

TECHNICAL FIELD

The present invention relates to an image display element including amicro light emitting element.

BACKGROUND ART

A display element in which a plurality of micro light emitting elementsconstituting pixels are arranged in a driving circuit substrate hasproposed. For example, in a technology disposed in PTL 1, a drivingcircuit is formed on a silicon substrate, and a minute light emittingdiode (LED) array that emits ultraviolet light is disposed on thedriving circuit. Alternatively, the technology discloses a small displayelement in which a wavelength conversion layer that converts ultravioletlight into visible light of red, green, and blue colors is provided onthe light emitting diode array, and thus a color image is displayed.

Such a display element has characteristics of high luminance and highdurability while being small. For this reason, the display element isexpected to be a display element for display devices such asglasses-like devices and head-up displays.

As a manufacturing method of such a display element, a method in which,since the material of the driving circuit substrate is different fromthe material of the micro light emitting element, the material of thedriving circuit substrate and the material of the micro light emittingelement are separately formed, and then are stuck to each other isgeneral. Regarding arrangement of an electrode in the micro lightemitting element, which has a large influence on the manufacturingmethod and manufacturing cost, various structures and manufacturingmethods thereof are proposed. For example, a case where electrodes inthe micro light emitting element are formed on different surfaces, asdisclosed in PTLs 1 and 2, a case where the electrodes in the microlight emitting element are formed on the same surface, as disclosed inPTL 3, or the like is exemplified.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No.2002-141492 (published on May 17, 2002)

[PTL 2] U.S. Patent Application Publication No. 2016/0276329 (publishedon Sep. 22, 2016)

[PTL 3] International Publication No. WO2017/094461 (published on Jun.8, 2017)

SUMMARY OF INVENTION Technical Problem

However, the structure of the micro light emitting element and thedisplay element disclosed in PTLs 1 and 2 described above has problemsas follows. Firstly, a large proportion (several tens of percent) oflight generated in a light emission layer of the micro light emittingelement is emitted from the side surface of the micro light emittingelement toward an adjacent micro light emitting element. Such light isabsorbed by the adjacent micro light emitting element and is emittedfrom this micro light emitting element again. Thus, optical crosstalk inwhich a micro light emitting element other than a micro light emittingelement which is originally to emit light appears to emit light.

In a case where micro light emitting elements are joined to each otherby a compound semiconductor, light is leaked to the adjacent micro lightemitting element through the compound semiconductor, and thus similaroptical crosstalk occurs. Such optical crosstalk causes a problem ofdegradation of contrast and degradation of color purity.

A large quantity of light is lost by light emission from the sidesurface of the micro light emitting element, and moreover, since lightis confined inside the micro light emitting element, a proportion oflight to be emitted to the outside to the light generated by the microlight emitting element is decreased, and thus a problem that lightemission efficiency is decreased occurs. Such decrease of lightextraction efficiency is a phenomenon occurring because the refractiveindex of the compound semiconductor constituting the micro lightemitting element is larger than refractive indices of air and resin. Aproblem of an increase of power consumption and an increase of atemperature by heat generation occurs by decreasing the light emissionefficiency.

An aspect of the present invention has been made considering theabove-described problems. An object of the present invention is toprevent the degradation of contrast and the degradation of color purityby preventing the occurrence of optical crosstalk between micro lightemitting elements adjacent to each other, and is to reduce powerconsumption by improving the light emission efficiency of the microlight emitting element.

Solution to Problem

To solve the above problems, (1) according to an embodiment of thepresent invention, a micro light emitting element includes a compoundsemiconductor in which a first conductive layer, a light emission layer,and a second conductive layer having a conductivity type opposite to aconductivity type of the first conductive layer are stacked in orderfrom a light emitting surface side. A first metal film electricallyconnected to the second conductive layer is disposed on a surface on anopposite side of the light emitting surface side. The first metal filmcovers the second conductive layer. A slope is formed around the lightemission layer. A first inclined angle of a first conductive layer sidesurface from the slope to the light emitting surface is larger than asecond inclined angle of the slope. The slope and the first conductivelayer side surface are covered together by a second metal film. A firsttransparent insulating film is disposed between the slope and the secondmetal film.

(2) According to the embodiment of the present invention, in the microlight emitting element, a second transparent insulating film is disposedbetween the first conductive layer side surface and the second metalfilm, in addition to the configuration of (1).

(3) According to the embodiment of the present invention, in the microlight emitting element, the second transparent insulating film isobtained by the first transparent insulating film extending between thefirst conductive layer side surface and the second metal film, inaddition to the configuration of (2).

(4) According to another embodiment of the present invention, a microlight emitting element includes a compound semiconductor in which afirst conductive layer, a light emission layer, and a second conductivelayer having a conductivity type opposite to a conductivity type of thefirst conductive layer are stacked in order from a light emittingsurface side. A first metal film electrically connected to the secondconductive layer is disposed on a surface on an opposite side of thelight emitting surface side. The first metal film covers the secondconductive layer. A slope is formed around the light emission layer. Theslope extends to the light emitting surface and is covered by a secondmetal film. A first transparent insulating film is disposed between theslope and the second metal film.

(5) According to the embodiment of the present invention, in the microlight emitting element, a third transparent insulating film is disposedbetween the second conductive layer and the first metal film, inaddition to the configuration of any of (1) to (4).

(6) According to the embodiment of the present invention, in the microlight emitting element, in plan view from an opposite side of the lightemitting surface side, the second metal film is disposed to overlap thefirst metal film, in addition to the configuration of any of (1) to (5).

(7) According to the embodiment of the present invention, in the microlight emitting element, a film thickness of the first transparentinsulating film is equal to or more than 75 nm, in addition to theconfiguration of any of (1) to (6).

(8) According to the embodiment of the present invention, in the microlight emitting element, the film thickness of the first transparentinsulating film is equal to or more than 400 nm, in addition to theconfiguration of any of (1) to (7).

(9) According to the embodiment of the present invention, in the microlight emitting element, the second inclined angle is equal to or lessthan 60° , in addition to the configuration of any of (1) to (3).

(10) According to the embodiment of the present invention, in the microlight emitting element, the second inclined angle is equal to or lessthan 50° , in addition to the configuration of any of (1) to (3).

(11) According to the embodiment of the present invention, in the microlight emitting element, the first metal film includes a layer containingsilver or aluminum as a main component, on the compound semiconductorside, in addition to the configuration of any of (1) to (10).

(12) According to the embodiment of the present invention, in the microlight emitting element, the second metal film includes a layercontaining silver or aluminum as a main component, on the compoundsemiconductor side, in addition to the configuration of any of (1) to(11).

(13) According to the embodiment of the present invention, in the microlight emitting element, the first transparent insulating film is an SiO₂film, in addition to the configuration of any of (1) to (12).

(14) According to the embodiment of the present invention, in the microlight emitting element, the first inclined angle is less than 900, inaddition to the configuration of any of (1) to (3).

(15) According to the embodiment of the present invention, in the microlight emitting element, the second metal film is electrically connectedto the first conductive layer, in addition to the configuration of anyof (1) to (14).

(16) According to the embodiment of the present invention, the microlight emitting element further includes a second electrode electricallyconnected to the second metal film, on an opposite side of the lightemitting surface side, in addition to the configuration of (15).

(17) According to the embodiment of the present invention, the microlight emitting element further includes a light emitting surface-sideelectrode configured from a transparent conductive film electricallyconnected to the first conductive layer, on a surface of the firstconductive layer on the light emitting surface side, in addition to theconfiguration of any of (1) to (14).

(18) According to the embodiment of the present invention, an imagedisplay element has a pixel region in which micro light emittingelements are arranged on a driving circuit substrate in atwo-dimensional array shape, in addition to the configuration of any of(1) to (17). A surface of the micro light emitting element on anopposite side of the light emitting surface side faces a surface of thedriving circuit substrate. First driving electrodes for supplying acurrent to the micro light emitting elements are arranged in atwo-dimensional array shape on a surface of the driving circuitsubstrate in the pixel region. A first electrode and the first drivingelectrode are connected in a one-to-one relation.

(19) According to the embodiment of the present invention, an imagedisplay element has a pixel region in which micro light emittingelements are arranged on a driving circuit substrate in atwo-dimensional array shape, in addition to the configuration of (17). Asurface of the micro light emitting element on an opposite side of thelight emitting surface side faces a surface of the driving circuitsubstrate. First driving electrodes for supplying a current to the microlight emitting elements are arranged in a two-dimensional array shape ona surface of the driving circuit substrate in the pixel region. A firstelectrode and the first driving electrode are connected in a one-to-onerelation. A second driving electrode is disposed on a surface of thedriving circuit substrate on an outside of the pixel region. The seconddriving electrode is electrically connected to the light emittingsurface-side electrode.

(20) According to the embodiment of the present invention, an imagedisplay element has a pixel region in which micro light emittingelements are arranged on a driving circuit substrate in atwo-dimensional array shape, in addition to the configuration of (16). Asurface of the micro light emitting element on an opposite side of thelight emitting surface side faces a surface of the driving circuitsubstrate. First driving electrodes and second driving electrodes forsupplying a current to the micro light emitting elements are arranged ina two-dimensional array shape on a surface of the driving circuitsubstrate in the pixel region. A first electrode and the first drivingelectrode are connected in a one-to-one relation. The second electrodeand the second driving electrode are connected to each other.

Advantageous Effects of Invention

It is possible to prevent the degradation of contrast and thedegradation of color purity by preventing the occurrence of opticalcrosstalk between micro light emitting elements adjacent to each other,and to reduce power consumption by improving the light emissionefficiency of the micro light emitting element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a schematic sectional view of an image display elementaccording to Embodiment 1 of the present invention, FIG. 1(b) is aschematic sectional view of a micro light emitting element according toEmbodiment 1 of the present invention, and FIG. 1(c) is a schematic planview of the micro light emitting element according to Embodiment 1 ofthe present invention.

FIGS. 2(a) to (g) are schematic sectional views illustrating amanufacturing flow of the micro light emitting element according toEmbodiment 1 of the present invention.

FIGS. 3(a) to 3(e) are schematic sectional views illustrating amanufacturing flow of the image display element according to Embodiment1 of the present invention.

FIG. 4(a) is an aerial view of the micro light emitting element having arectangular parallelepiped structure, and FIG. 4(b) is an aerial view ofthe micro light emitting element 100 having a truncated bent pyramidtype structure according to Embodiment 1 of the present invention.

FIG. 5 is a diagram illustrating a simulation result of film thicknessdependency of a transparent insulating film in light extractionefficiency.

FIGS. 6(a) to 6(e) are diagrams illustrating simulation results ofdependency of the light extraction efficiency on dimensions and anglesof each unit in the image display element illustrated in FIG. 1(a).

FIG. 7 is a schematic sectional view of an image display elementaccording to Embodiment 2 of the present invention.

FIGS. 8(a) to 8(d) are schematic sectional views illustrating amanufacturing flow of the image display element according to Embodiment2 of the present invention.

FIG. 9(a) is a schematic sectional view of an image display elementaccording to Embodiment 3 of the present invention, and FIG. 9(b) is aschematic plan view of a micro light emitting element according toEmbodiment 3 of the present invention.

FIGS. 10(a) to 10(g) are schematic sectional views illustrating amanufacturing flow of the image display element according to Embodiment3 of the present invention.

FIG. 11 is a schematic sectional view of an image display elementaccording to Embodiment 4 of the present invention.

FIGS. 12(a) to 12(f) are schematic sectional views illustrating amanufacturing flow of the image display element according to Embodiment4 of the present invention.

FIG. 13 is a schematic sectional view of an image display elementaccording to Embodiment 5 of the present invention.

FIGS. 14(a) to 14(e) are schematic sectional views illustrating amanufacturing flow of the image display element according to Embodiment5 of the present invention.

FIG. 15(a) to 15(f) are diagrams illustrating simulation results ofdependency of the light extraction efficiency on the dimensions and theangles of each unit in the image display element illustrated in FIG. 13.

FIGS. 16(a) to 16(d) are schematic sectional views illustrating amanufacturing flow of an image display element according to Embodiment 6of the present invention.

FIGS. 17(a) to 17(d) are schematic sectional views illustrating amanufacturing flow of an image display element according to Embodiment 7of the present invention.

FIG. 18(a) is an aerial view of a micro light emitting element having atruncated pyramid type structure according to Embodiment 8 of thepresent invention, FIG. 18(b) is a diagram illustrating a simulationresult of dependency of the light extraction efficiency on an inclinedangle, and FIG. 18(c) is a diagram illustrating a simulation result ofthe film thickness dependency of a transparent insulating film in thelight extraction efficiency.

FIG. 19 is a schematic sectional view of an image display elementaccording to Embodiment 9 of the present invention.

FIGS. 20(a) to 20(f) are schematic sectional views illustrating amanufacturing flow of a micro light emitting element according toEmbodiment 9 of the present invention.

FIGS. 21(a) to 21(c) are schematic sectional views illustrating amanufacturing flow of the image display element according to Embodiment9 of the present invention.

FIGS. 22(a) to 22(f) are schematic sectional views illustrating amanufacturing flow of a micro light emitting element according toEmbodiment 10 of the present invention.

FIGS. 23(a) to 23(j) are schematic sectional views illustrating amanufacturing flow of a micro light emitting element according toEmbodiment 11 of the present invention.

FIGS. 24(a) to 24(i) are schematic sectional views illustrating amanufacturing flow of a micro light emitting element according toEmbodiment 12 of the present invention.

DESCRIPTION OF EMBODIMENTS Embodiment 1

(Configuration of Image Display Element 200)

FIG. 1(a) is a schematic sectional view of an image display element 200according to Embodiment 1 of the present invention. FIG. 1(b) is aschematic sectional view of a micro light emitting element 100 accordingto Embodiment 1 of the present invention. FIG. 1(c) is a schematic planview of the micro light emitting element 100 according to Embodiment 1of the present invention. The image display element 200 including aplurality of micro light emitting elements 100 will be described below,as an example, with reference to FIGS. 1 to 6. In descriptions of theconfiguration of the image display element 200, a light emitting surfaceis referred to as an upper surface, a surface on an opposite side of thelight emitting surface side is referred to as a lower surface, andsurfaces on sides other than the upper surface and the lower surface arereferred to as side surfaces.

As illustrated in FIG. 1(a), the image display element 200 includes theplurality of micro light emitting elements 100 and a driving circuitsubstrate 50. The driving circuit substrate 50 supplies a current to themicro light emitting element 100 in a pixel region 1 to control lightemission. The pixel region 1 is a region in which the micro lightemitting elements 100 are arranged on the driving circuit substrate 50in a two-dimensional array shape. The image display element 200 has thepixel region 1.

The micro light emitting element 100 emits light to the opposite side ofthe driving circuit substrate 50. A wavelength conversion layer, a lightdiffusion layer, a color filter, a micro-lens, and the like may bearranged on the light emitting surface side in the micro light emittingelement 100. These components are not directly related to one form ofthe present invention, and thus are not illustrated in the drawings.

The driving circuit substrate 50 is configured by a micro light emittingelement driving circuit, a row selection circuit, a column signal outputcircuit, an image processing circuit, an input and output circuit, andthe like. The micro light emitting element driving circuit controls acurrent to be supplied to each micro light emitting element 100. The rowselection circuit selects each row of the micro light emitting elements100 arranged in a two-dimensional matrix shape. The column signal outputcircuit outputs a light emitting signal to each column. The imageprocessing circuit calculates the light emitting signal based on aninput signal.

A P-drive electrode (first driving electrode) 51 connected to the microlight emitting element 100 and an N-drive electrode (second drivingelectrode) 52 are disposed on a surface of the driving circuit substrate50 on a bonding surface side. That is, the surface of the drivingcircuit substrate 50 faces a surface of the micro light emitting element100 on an opposite side of the light emitting surface side. In FIG. 1,the driving circuit substrate 50 is a silicon substrate (semiconductorsubstrate) in which an LSI is formed, but other form of the drivingcircuit substrate such as glass substrate with TFT circuit is alsopossible. Since the driving circuit substrate can be manufactured by awell-known technology, detailed descriptions of the function and theconfiguration thereof will not be made.

P-drive electrodes 51 for supplying a current to the micro lightemitting elements 100 are arranged on the surface of the pixel region 1in the driving circuit substrate 50 in a two-dimensional array shape.Alternatively, the N-drive electrode 52 is disposed on the surface(surface of an N connection region 3) of the driving circuit substrate50 on the outside of the pixel region 1. The N-drive electrode 52 iselectrically connected to a common N-electrode (light emittingsurface-side electrode) 40 through a metal reflective layer 20W.

Various planar shapes such as a rectangle, a polygon, a circle, and anellipse may be provided as the shape of the micro light emitting element100. The longest length of the micro light emitting element 100 in alongitudinal direction of the upper surface is equal to or less than 60μm. Regarding the image display element 200, 3000 or more micro lightemitting elements 100 are integrated in the pixel region 1.

The micro light emitting element 100 includes a compound semiconductor14. Generally, the compound semiconductor 14 is configured in a mannerthat an N-side layer (first conductive layer) 11, a light emission layer12, and a P-side layer (second conductive layer) 13 are stacked in orderfrom the light emitting surface side. The P-side layer 13 has aconductivity type opposite to the conductivity type of the N-side layer11.

For example, in a case where the micro light emitting element 100 emitslight in a wavelength band from ultraviolet light to a green color, thecompound semiconductor 14 is a semiconductor of a nitride semiconductor(AlInGaN series). In a case where the micro light emitting element 100emits light in a wavelength band from a yellow color to a red color, thecompound semiconductor 14 is an AlInGaP-based semiconductor.Alternatively, in a case where the micro light emitting element 100emits light in a wavelength band from the red color to infrared light,the compound semiconductor 14 is an AlGaAs-based or GaAs-basedsemiconductor. Depending on wavelength, other material such as quantumdot of CdSe or InP and Perovskite nanocrystal can be used as thecompound semiconductor 14.

The configuration of the compound semiconductor 14, in which the N-sidelayer 11 is disposed on the light emitting surface side will bedescribed below. However, a configuration in which the P-side layer 13is disposed on the light emitting surface side may be made. Normally,each of the N-side layer 11, the light emission layer 12, and the P-sidelayer 13 is optimized by including a plurality of layers instead of asingle layer. However, this is not directly related to the form of thepresent invention, and thus detailed descriptions of the detailedstructure of each of the N-side layer 11, the light emission layer 12,and the P-side layer 13 are not made.

Normally, the light emission layer 12 is interposed between an N-typelayer and a P-type layer. However, a case where the N-type layer and theP-type layer include a non-doped layer or a layer having dopants ofopposite conductivity may be provided. For this reason, the N-type layerand the P-type layer will be described below as an N-side layer and aP-side layer, respectively.

The surface of the driving circuit substrate 50 is a bonding surfacebonded to the plurality of micro light emitting elements 100, and theplurality of micro light emitting elements 100 are stuck to the surface.In the embodiment, the micro light emitting element 100 is a so-calledvertical type. The micro light emitting element 100 includes aP-electrode (first electrode) 20P on the lower surface and includes acommon N-electrode 40 on the upper surface.

Specifically, in the micro light emitting element 100, the commonN-electrode 40 is disposed on the light emitting surface side, and theP-electrode 20P is disposed on the surface on an opposite side of thelight emitting surface side. The light emitting surface of the microlight emitting element 100 is the upper surface of the micro lightemitting element 100. The side opposite to the light emitting surface isa lower side of the micro light emitting element 100, on which theP-electrode 20P is disposed. The P-electrode 20P and the P-driveelectrode 51 are connected in a one-to-one relation.

In the pixel region 1, the P-electrode 20P connected to the P-side layer13 is disposed on the lower surface of the micro light emitting element100. The P-electrode 20P is connected to the P-drive electrode 51 on thedriving circuit substrate 50 through a bonding material 70, and thustransmits a current supplied from the driving circuit substrate 50 tothe P-side layer 13.

The current passing through the P-side layer 13 further passes throughthe light emission layer 12 and the N-side layer 11 to flow to thecommon N-electrode 40. The current flows to the N-drive electrode 52 ofthe driving circuit substrate 50 in the N connection region 3 on theoutside of the pixel region 1. In this manner, the micro light emittingelement 100 emits light at predetermined intensity, in accordance withthe current amount supplied by the driving circuit substrate 50.

Alternatively, in FIG. 1, in order to connect the common N-electrode 40and the N-drive electrode 52 by the same structure as the structure ofconnecting the P-electrode 20P and the P-drive electrode 51, a dummyconnection element 101 configured with the same material as the materialof the micro light emitting element 100 is used. With such aconfiguration, it is possible to simplify a connection process betweenthe micro light emitting element 100 and the driving circuit substrate50. A connection method between the common N-electrode 40 and theN-drive electrode 52 may be different from a connection method betweenthe P-electrode 20P and the P-drive electrode 51. Alternatively, thedummy connection element 101 may be processed to be a rod extending in adepth direction of the paper surface in FIG. 1(a) or 1(b).

The lower surface of the P-side layer 13 is in contact with a P-sidemetal layer (first metal film) 10. The P-side metal layer 10 has a needto reflect light reaching the lower surface of the P-side layer 13upward with high efficiency, and thus preferably covers most of thelower surface of the P-side layer 13. The P-side metal layer 10 preventsdownward emission of light. The P-side metal layer 10 is disposed on asurface on the opposite side of the light emitting surface side and iselectrically connected to the P-electrode 20P and the P-side layer 13.The P-side metal layer 10 covers the P-side layer 13 from the surface onthe opposite side of the light emitting surface side.

The P-side metal layer 10 may be configured by a single layer or aplurality of layers. Preferably, a metal layer having high reflectivityfor visible light is disposed on a side of the P-side metal layer 10,which is in contact with the P-side layer 13. For example, the P-sidemetal layer 10 includes a metal layer M1 containing silver or aluminumas the main component, on the P-side layer 13 side. In order to realizea favorable ohmic contact between the metal layer M1 and the P-sidelayer 13, metal such as palladium or nickel may be partially arranged,or a very thin metal film of palladium, nickel, or the like may bedisposed.

The common N-electrode 40 is formed from a transparent conductive layer,that is, a transparent conductive film electrically connected to theN-side layer 11. The common N-electrode 40 may be an oxide semiconductorsuch as indium tin oxide (ITO) and indium zinc oxide (IZO) or may be asilver nanofiber layer.

Alternatively, the common N-electrode 40 may be a mesh-like metal thinfilm disposed at the upper portion of a filling material 60. The microlight emitting element 100 includes the common N-electrode 40 on thesurface of the N-side layer 11 on the light emitting surface side. Anisolation trench 18 formed between the plurality of micro light emittingelements 100 is filled with the filling material 60.

The micro light emitting elements 100 are separately divided by theisolation trench 18. For this reason, it is possible to prevent lightleakage between the micro light emitting elements 100 adjacent to eachother. The entire periphery of the side surface of the light emissionlayer 12 constitutes a portion of a slope 16S. That is, the slope 16S isformed around the light emission layer 12. The slope 16S constitutes aportion of the side surface of the N-side layer 11, the entire peripheryof the side surface of the light emission layer 12, and the entireperiphery of a portion of the side surface of the P-side layer 13. Asillustrated in FIG. 1(c), in a case where a planar shape of the microlight emitting element 100 is rectangular, a portion of the periphery ofthe side surface of one micro light emitting element 100 constitutesfour slopes 16S. Preferably, all the side surfaces of the P-side layer13 are inclined similar to the light emission layer 12. However, thelower surface of the P-side layer 13 may be bent from the slop 16Sdepending on a manufacturing flow.

In the embodiment, a case where the planar shape of the micro lightemitting element 100 is rectangular will be described. However, in acase where the planar shape of the micro light emitting element 100 ispolygonal, a plurality of slopes 16S are formed. Specifically, in a casewhere N corners (N is a natural number) of a polygon being the planarshape of the micro light emitting element 100 are provided, N pieces ofslopes 16S are formed.

Alternatively, in a case where the planar shape of the micro lightemitting element 100 is circular, the slope 16S is formed by a truncatedconical side surface. An inclined angle (second inclined angle) θe ofthe slope 16S is approximately 40° to 55°, and preferably 35° to 60° inconsideration of manufacturing variations. The inclined angle θe is anangle formed by the slope 16S and a horizontal surface (upper surface)S1 of the light emission layer 12.

As illustrated in FIG. 1(b), the slope 16S extends from the side surfaceof the P-side layer 13 to a portion of the side surface of the N-sidelayer 11. However, the slope 16S does not reach the light emittingsurface, that is, the upper surface of the micro light emitting element100. The portion of the side surface of the N-side layer 11 constitutesan N-side layer side surface (first conductive layer side surface) 11S.The N-side layer side surface 11S extends from the slope 16S to thelight emitting surface.

The inclined angle (first inclined angle) θb of the N-side layer sidesurface 11S is an angle larger than the inclined angle θe. The inclinedangle θb is less than 90°, and preferably small.

In a case where the horizontal surface S1 of the light emission layer 12is parallel to the horizontal surface (upper surface) S2 of the N-sidelayer 11, the inclined angle θb is an angle formed by the N-side layerside surface 11S and the horizontal surface S2 of the N-side layer 11.In a case where the horizontal surface S1 of the light emission layer 12is not parallel to the horizontal surface S2 of the N-side layer 11, theinclined angle θb is an angle formed by the N-side layer side surface11S and the horizontal surface S2 of the N-side layer 11.

However, in a case where the size of the micro light emitting element100 is small (for example, in a case where the long side of the uppersurface of the micro light emitting element 100 is equal to or less than10 μm), if the inclined angle θb is reduced, the area of the horizontalsurface of the light emission layer 12 is reduced. If the area of thehorizontal surface of the light emission layer 12 is reduced, currentdensity of a current passing through the light emission layer 12 mayincrease, and thus internal quantum efficiency may decrease. Thus, theinclined angle θb is preferably about 700 to 850.

The slope 16S and the N-side layer side surface 11S are covered by atransparent insulating film (first transparent insulating film) 17. Thetransparent insulating film 17 is covered by a metal reflective layer(second metal film) 20W. That is, the slope 16S and the N-side layerside surface 11S are covered together by the metal reflective layer 20W.The transparent insulating film 17 is transparent to visible light aswith SiO₂, and a material having a refractive index which is less thanthe refractive index of the compound semiconductor 14 is preferable.

The transparent insulating film 17 is disposed between the slope 16S andthe metal reflective layer 20W. The transparent insulating film 17extends between the N-side layer side surface 11S and the metalreflective layer 20W. Here, a portion of the transparent insulating film17, which is disposed between the slope 16S and the metal reflectivelayer 20W is referred to as a first transparent insulating film. Aportion thereof, which is disposed between the N-side layer side surface11S and the metal reflective layer 20W is referred to as a secondtransparent insulating film. In this case, the second transparentinsulating film is set to be obtained by the first transparentinsulating film extending between the N-side layer side surface 11S andthe metal reflective layer 20W. That is, the first transparentinsulating film and the second transparent insulating film areintegrally formed. The film thickness of the transparent insulating film17 is preferably equal to or more than 75 nm, and more preferably equalto or more than 400 nm, in particular.

The metal reflective layer 20W may be configured by a single layer or aplurality of layers. Preferably, the metal reflective layer 20W includesa metal layer M2 on the transparent insulating film 17 side, that is, onthe compound semiconductor 14 side. The metal layer M2 contains silveror aluminum having high reflectivity for visible light, as the maincomponent. The metal reflective layer 20W has a need to shield light,and thus the entire thickness thereof is preferably several tens or moreof nm. The same material is used for the P-electrode 20P and the metalreflective layer 20W in order to simplify a manufacturing flow. However,different materials may be used.

In plan view from a side opposite to the light emitting surface side,the metal reflective layer 20W is preferably disposed to overlap theP-side metal layer 10. In plan view from a side opposite to the lightemitting surface, if a space is provided between the metal reflectivelayer 20W and the P-side metal layer 10, light is emitted from the spaceto the outside, and this causes optical crosstalk. Thus, preferably,there is no space. The filling material 60 may be a transparentmaterial.

Since a situation in which light is emitted from the micro lightemitting element 100 in a bottom surface direction and a side surfacedirection does not occur by the metal reflective layer 20W and theP-side metal layer 10, it is possible to prevent the occurrence ofoptical crosstalk even though the filling material 60 is transparentresin. In a micro light emitting element in the related art, theoccurrence of optical crosstalk is prevented by the filling material,but it is difficult to completely prevent the occurrence of opticalcrosstalk by bubbles appeared in the filling material.

Alternatively, in the micro light emitting element in the related art,it is necessary to use a special material such as a light absorbingmaterial like carbon black or a white resin containing TiO₂ particles,as the filling material. Thus, it is necessary to increase a fillingtime for preventing generation of bubbles in the filling material. Forthis reason, the filling material is expensive, and thus manufacturingcost increases.

However, in the form of the present invention, it is easy to performmaterial selection of the filling material 60 and to product the fillingmaterial 60. Thus, it is possible to decrease manufacturing cost incomparison to a case of manufacturing the micro light emitting elementin the related art.

(Manufacturing Flow of Micro Light Emitting Element 100)

Next, the manufacturing flow of the micro light emitting element 100will be described with reference to FIGS. 2(a) to 2(g). FIGS. 2(a) to2(g) are schematic sectional views illustrating the manufacturing flowof the micro light emitting element 100 according to Embodiment 1 of thepresent invention. In descriptions of the manufacturing flow of themicro light emitting element 100, the P-side metal layer 10 side is setto be upper, and a growth substrate 9 side is set to be lower.

A sectional view of the pixel region 1 is illustrated on the right sidein FIGS. 2(a) to 2(g), and a sectional view of the N connection region 3is illustrated on the left side in FIGS. 2(a) to 2(g). As illustrated inFIG. 2(a), the compound semiconductor 14 is formed by sequentiallystacking the N-side layer 11, the light emission layer 12, and theP-side layer 13 on the growth substrate 9. The P-side metal layer 10 isfurther deposited on the compound semiconductor 14.

After the P-side metal layer 10 is deposited on the compoundsemiconductor 14, as illustrated in FIG. 2(b), a separation trench 15 isformed by etching portions of the P-side metal layer 10, the P-sidelayer 13, the light emission layer 12, and the N-side layer 11. At thistime, a portion including the light emission layer 12 serves as a mesa16. The mesa 16 is configured by the N-side layer 11, the light emissionlayer 12, the P-side layer 13, and the P-side metal layer 10. Asillustrated in FIG. 1(c), when viewed from the upper surface, theseparation trench 15 is formed at equal intervals in an up-down and aright-left direction. The shape of the mesa 16 is a shape of a truncatedpyramid.

The shape of the mesa 16 is not limited to a truncated pyramid and maybe a truncated cone or another truncated polygon. In the pixel region 1,the separation trench 15 separates the micro light emitting elements 100from each other. And, in the N connection region 3, an N-contact trench15N is formed simultaneous with the separation. An N-contact hole 19N isformed later in the N-contact trench 15N.

The slope 16S as the side surface of the mesa 16 is formed and processedsuch that the inclined angle θe as the angle formed by the slope 16S andthe horizontal surface of the light emission layer 12 is, for example,500. Preferably, the slope 16S is formed such that the inclined angle θeis 40° to 55°. The slope 16S reflects light traveling in a directionparallel to the horizontal surface of the light emission layer 12, whichoccupies a large part of light emitted from the light emission layer 12,toward the light emitting surface. Thus, it is possible to increaselight extraction efficiency of the micro light emitting element 100.

In a case where the slope 16S is perpendicular to the horizontal surfaceof the light emission layer 12, light emitted in the direction parallelto the horizontal surface of the light emission layer 12 repeatsreflection, and thereby is not emitted to the outside. If the inclinedangle θe deviates from 450 largely, an incident angle of light, which isemitted from the light emission layer 12 and is incident to the lightemitting surface, becomes too large, when the light is emitted from thelight emission layer 12 and reflected by the slope 16S. Thus, totalreflection occurs on the light emitting surface, and the light is notemitted to the outside. The inclined angle θe may be different for eachof the plurality of side surfaces of the mesa 16. In this case, aplurality of inclined angles θe is provided. The minimum angle of theplurality of inclined angles θe is preferably 400 to 550, and furtherpreferably, all the inclined angles θe are 40° to 55°.

After the separation trench 15 is formed, as illustrated in FIG. 2(c),an isolation trench 18 that divides the compound semiconductor 14 of themicro light emitting element 100 is formed. The side surface of theN-side layer 11, which is formed by the isolation trench 18 is theN-side layer side surface 11S. The N-side layer side surface isprocessed and formed such that the inclined angle θb as an angle formedby the N-side layer side surface 11S and the horizontal surface of thegrowth substrate 9 is, for example, 80°. Preferably, the N-side layerside surface 11S is formed such that the inclined angle θb is 700 to850. That is, the inclined angle θb is preferably larger than theinclined angle θe.

In order to improve light extraction efficiency of the micro lightemitting element 100, preferably, the inclined angle θb is as small aspossible in an angle range of being larger than the inclined angle θe.In the subsequent process, the growth substrate 9 is separated, and thusan interface between the N-side layer 11 and the growth substrate 9 orthe processed surface of the N-side layer 11 serves as the lightemitting surface. Thus, the inclined angle θb is equal to an angleformed by the N-side layer side surface 11S and the light emittingsurface.

In FIG. 2(c), the isolation trench 18 reaches the growth substrate 9,but the N-side layer 11 having a predetermined thickness may remain.That is, the isolation trench 18 may not reach the growth substrate 9.In FIG. 3(c) as the subsequent process, after the growth substrate 9 isseparated, the remaining N-side layer 11 is removed by etching,polishing, and the like. Thus, as illustrated in FIG. 1(a), it ispossible to individually separate the micro light emitting elements 100from each other.

The shape of the micro light emitting element 100 is important in astate where the image display element 200 is formed. Temporary shape ofthe micro light emitting element in the middle of the manufacturing flowis not important. The inclined angle θb of the N-side layer side surface11S may be different for each of a plurality of side surfaces of theN-side layer 11. In this case, a plurality of inclined angles θb isprovided. The minimum angle of the plurality of inclined angles θb ispreferably 700 to 850, and further preferably, all the inclined angle θbare 700 to 850.

After the isolation trench 18 is formed, as illustrated in FIG. 2(d),the transparent insulating film 17 is deposited to cover the exposedportions of the growth substrate 9, the N-side layer 11, the lightemission layer 12, the P-side layer 13, and the P-side metal layer 10.Here, a SiO₂ film having a thickness of 400 nm is deposited as thetransparent insulating film 17 by a CVD method. Films of SiN, SiON, andSiCO or a film obtained by stacking the above films may be provided asthe transparent insulating film 17 in place of the SiO₂ film.Preferably, the transparent insulating film 17 is formed by the CVDmethod such that the thickness of the transparent insulating film 17that covers the side surface of the micro light emitting element 100 isuniform.

After the transparent insulating film 17 is deposed, as illustrated inFIG. 2(e), a P-contact hole 19P is formed in the mesa 16 of the pixelregion 1, and an N-contact hole 19N is formed in the N-contact trench15N of the N connection region 3. Specifically, the N-contact hole 19Nis formed by removing the transparent insulating film 17 on the N-sidelayer 11 in the N-contact trench 15N. At this time, a bottom opening 19Bmay be formed in the transparent insulating film 17 deposited on thebottom of the isolation trench 18. The P-contact hole 19P reaches theP-side metal layer 10, and the N-contact hole 19N reaches the N-sidelayer 11 of the N-contact trench 15N.

Further, as illustrated in FIG. 2(f), the metal layer 20 is deposited onthe transparent insulating film 17. Then, as illustrated in FIG. 2(g),the metal layer 20 is patterned. Thus, the metal layer 20 is processedto serve as the P-electrode 20P on the P-contact hole 19P, to serve asthe metal reflective layer 20W in the periphery of the isolation trench18, and to serve as the N-electrode (second electrode) 20N in the Nconnection region 3.

As described above, the micro light emitting element 100 is formed by avery simple manufacturing flow in which a process of depositing thetransparent insulating film 17 is performed once, a process of formingthe metal layer 20 is performed twice, and a photolithographic processis performed four times. Further, the dummy connection element 101 isformed in the N connection region 3, and thus a connection with thedriving circuit substrate 50 becomes simple as described later.

(Manufacturing Flow of Image Display Element 200)

Next, the manufacturing flow of the image display element 200 will bedescribed using FIG. 3. FIGS. 3(a) to 3(e) are schematic sectional viewsillustrating the manufacturing flow of the image display element 200according to Embodiment 1 of the present invention. In descriptions ofthe manufacturing flow of the image display element 200, the growthsubstrate 9 side is set to be upper, and the driving circuit substrate50 side is set to be lower.

As illustrated in FIG. 3(a), firstly, the driving circuit substrate 50is manufactured. The driving circuit substrate 50 is formed on, forexample, a single crystal silicon substrate (wafer) by a general CMOSprocess. Here, each of the micro light emitting element 100 and thedriving circuit substrate 50 may be in a wafer state, and the microlight emitting element 100 may be divided in a unit of the image displayelement 200. Alternatively, both the micro light emitting element 100and the driving circuit substrate 50 may be divided in a unit of theimage display element 200.

After the driving circuit substrate 50 is manufactured, as illustratedin FIG. 3(b), the micro light emitting element 100 and the dummyconnection element 101 are stuck to the driving circuit substrate 50.The bonding material 70 is formed on the P-drive electrode 51 and theN-drive electrode 52 of the driving circuit substrate 50. The P-driveelectrode 51 and the N-drive electrode 52 are physically andelectrically connected to the P-electrode 20P and the N-electrode 20Nthrough the bonding material 70, respectively. At this time, theP-electrode 20P and the N-electrode 20N are precisely aligned to overlapthe corresponding P-drive electrode 51 and N-drive electrode 52.

The bonding material 70 is a conductive connection member and is a goldbump, a conductive paste of gold or silver, an anisotropic conductivefilm (ACF), or nanoparticles of gold, silver, palladium, or the like.The bonding material 70 can be omitted when the P-electrode 20P and theP-drive electrode 51 can be bonded directly. As illustrated in FIG.3(c), the growth substrate 9 is separated to be removed. Various methodssuch as grinding, polishing, plasma etching, wet etching, sacrificiallayer wet etching, and laser lift-off can be used to remove the growthsubstrate 9. At this time, processing, for example, removing of aportion of the N-side layer 11 may be performed.

After the growth substrate 9 is removed, as illustrated in FIG. 3(d), aspace between the micro light emitting elements 100 is filled with thefilling material 60. Here, for example, transparent silicon resin isused as the filling material 60. Dry etching, wet washing, and the likeare performed to expose the N-side layer 11 of the micro light emittingelement 100. Then, as illustrated in FIG. 3(e), the common N-electrode40 is deposited to cover the exposed portions of the N-side layer 11,the transparent insulating film 17, the metal reflective layer 20W, andthe filling material 60. Here, for example, an ITO film is used as thecommon N-electrode 40. With the above-described processes, the imagedisplay element 200 is formed.

(Light Emission Efficiency of Micro Light Emitting Element 100)

Light emission efficiency of the micro light emitting element 100 formedin a manner as described above was evaluated. Regarding the micro lightemitting element 100, the arrangement pitch is 10 μm, the shape is asquare, the inclined angle θb is 800, the inclined angle θe is 500, thethickness of the P-side layer 13 is 100 nm, and the thickness of theN-side layer 11 is 6 m. In addition, the size of the upper surface ofthe N-side layer 11 is 8 μm×8 μm, and the depth D at a portion occupiedby the N-side layer 11 in the slope 16S is 1 μm.

The depth D is a depth in the vertical direction (direction from theupper surface of the micro light emitting element 100 toward the lowersurface). The compound semiconductor 14 is a nitride semiconductor. TheN-side layer 11 is a GaN layer. The light emission layer 12 is amultiple quantum well layer with InGaN and GaN. The peak wavelength oflight emitted from the light emission layer 12 is 450 nm.

FIG. 4(a) is an aerial view of the micro light emitting element having arectangular parallelepiped structure. FIG. 4(b) is an aerial view of themicro light emitting element 100 having a truncated bent pyramid typestructure according to Embodiment 1 of the present invention. The microlight emitting element having the rectangular parallelepiped structureillustrated in FIG. 4(a) and the micro light emitting element 100 havinga truncated bent pyramid type structure illustrated in FIG. 4(b)according to Embodiment 1 of the present invention were compared to eachother.

In all cases of FIG. 4(a) and FIG. 4(b), the size of the upper surfaceof the N-side layer 11 was 8 μm×8 μm, and the same compoundsemiconductor was used. In the cases of FIG. 4(a) and FIG. 4(b), theconstituent materials and the formation processes are the same as eachother except for a different shape. In the case of FIG. 4(a), theseparation trench and the isolation trench were processed to be inclinedas small as possible.

In all the cases, a transparent resin layer containing a scatteringmaterial was disposed on the upper surface of the N-side layer. Inaddition, in all the cases, 10000 pieces of micro light emittingelements in 100 rows×100 columns were simultaneously turned on, so as toevaluate total luminous flux intensity. The current amount per one microlight emitting element 100 is 5 μA. The following Table 1 showsmeasurement results.

TABLE 1 Rectangular Truncated bent parallelepiped pyramid structure typestructure External quantum efficiency 12% 43% Area ratio of lightemission layer 100%  32% to light emitting surface Estimated effectiveinternal 66% 53% quantum efficiency

As shown in Table 1, in the truncated bent pyramid type structure inFIG. 4(b), external quantum efficiency is 3.6 times that of the simplerectangular parallelepiped structure in FIG. 4(a). In the truncated bentpyramid type structure in FIG. 4(b), even though the area of the lightemission layer is about ⅓ of the area of the rectangular parallelepipedstructure in FIG. 4(a), large improvement is achieved. To investigateroot cause of the improvement, the light extraction efficiency wassimulated with a lay trace method. The following Table 2 shows results.Estimated effective internal quantum efficiency in Table 1 is anestimated value obtained by being calculated from the external quantumefficiency in Table 1 with the light extraction efficiency in Table 2.Values shown in Table 2 are simulation values.

TABLE 2 Rectangular Truncated bent parallelepiped pyramid structure typestructure Light extraction efficiency 17.9% 80.7% Side surfaceabsorption 29.4% 8.8% Bottom surface absorption 29.5% 6.0% Internalabsorption 23.2% 4.5% Average internal reflection 85.4 25.4 number

The light extraction efficiency indicates a proportion of the quantityof light emitted from the upper surface of the micro light emittingelement into the transparent resin layer. Side surface absorptionindicates a proportion of the quantity of light absorbed by the metalreflective layer 20W on the entire side surface of the micro lightemitting element. Bottom surface absorption indicates a proportion ofthe quantity of light absorbed by the P-side metal layer 10 on the lowersurface of the micro light emitting element. Internal absorptionindicates a proportion of the quantity of light absorbed again by thelight emission layer 12. The average internal reflection numberindicates an average of reflections in the compound semiconductor 14until light emitted from the light emission layer 12 is emitted to theoutside or is absorbed by the metal reflective layer 20W.

The tendency of the light extraction efficiency in Table 2 coincideswell with the tendency of the external quantum efficiency in Table 1. Itis considered that a difference in external quantum efficiency is themain cause of a difference in light extraction efficiency. Only lightincident to the upper surface of the micro light emitting element at anangle which is equal to or less than a critical total reflection angleis emitted to the outside from the upper surface of the micro lightemitting element. The critical total reflection angle is about 37° in acase of light which is incident from GaN to the transparent resin layer.

In the rectangular parallelepiped structure in FIG. 4(a), an incidentangle to the upper surface of the micro light emitting element isconstant regardless of the number of reflections therein. Thus, lightemitted from the light emission layer 12 in a horizontal direction isnot emitted to the outside. On the contrary, in the truncated bentpyramid type structure in FIG. 4(b), light emitted from the lightemission layer 12 in the horizontal direction is reflected upward by theslope 16S, is incident to the light emitting surface at an angle of thecritical total reflection angle or less, and then is emitted to theoutside.

Further, even in a case where light is not emitted to the outside in aninitial state when the light is emitted from the light emission layer12, every time the light is reflected by the N-side layer side surface11S, the incident angle of the light to the upper surface of the microlight emitting element 100 changes.

Therefore, light emitted from the light emission layer 12 repeatsinternal reflection, and then is emitted to the outside. Accordingly, itis possible to significantly improve the light extraction efficiency.

Next, in order to examine an influence of the transparent insulatingfilm 17, dependency of the light extraction efficiency on the filmthickness of the transparent insulating film 17 in the micro lightemitting element 100 according to one form of the present invention wassimulated. FIG. 5 illustrates results in a case of using SiO₂ as thetransparent insulating film 17. FIG. 5 is a diagram illustrating asimulation result of film thickness dependency on the transparentinsulating film 17 at the light extraction efficiency.

In FIG. 5, a horizontal axis indicates the film thickness, and avertical axis indicates light extraction efficiency. In a case where thetransparent insulating film 17 is not provided, the light extractionefficiency is 63%. Thus, in the truncated bent pyramid type structure inwhich the transparent insulating film 17 is not provided, lightextraction efficiency is much larger than that of the rectangularparallelepiped structure with the transparent insulating film 17. It isshown that the shape of the compound semiconductor 14 is very important.

The light extraction efficiency increases as the film thickness of thetransparent insulating film 17 becomes thicker. However, in a case wherethe film thickness of the transparent insulating film 17 is equal to ormore than 400 nm, the change is small. Thus, it is most preferable thatthe film thickness of the transparent insulating film 17 is equal to ormore than 400 nm. Since the decrease rate of the light extractionefficiency is within 5% if the film thickness is equal to or more than75 nm, the film thickness may be equal to or more than at least 75 nm.

As the effect by the transparent insulating film 17, it is considered toimprove reflectivity on the side surface of the micro light emittingelement 100 and to improve the light extraction efficiency. In therectangular parallelepiped structure, the effect by the transparentinsulating film 17 is very weak. The reason is considered as follows.Even though the reflectivity on the side surface of the micro lightemitting element having the rectangular parallelepiped structure isimproved, the angle incident to the upper surface of the micro lightemitting element is not changed. Thus, light which is totally reflectedby the upper surface is always reflected no matter how many times thelight is reflected at side surfaces, and the light extraction efficiencyis not improved. Thus, it is important that the micro light emittingelement 100 has the slope 16S and the inclined N-side layer side surface11S which allow the incident angle to the upper surface to change.

Next, FIG. 6 illustrates results obtained by examining the change of thelight extraction efficiency to the dimensions and the angles of eachunit in the micro light emitting element 100 with the simulation. FIGS.6(a) to 6(e) are diagrams illustrating simulation results of dependencyof the light extraction efficiency on the dimensions and the angles ofeach unit in the image display element 200 illustrated in FIG. 1(a).FIGS. 6(a) to 6(e) also illustrate ratios (area ratio) of the area ofthe light emission layer 12 to the area of the light emitting surface(upper surface of the N-side layer 11). In FIGS. 6(a) to 6(e), avertical axis indicates the light extraction efficiency or the arearatio.

In all cases in FIGS. 6(a) to 6(e), so long as particular statements arenot made, the size of the upper surface of the N-side layer 11 is 8 μm×8μm, the thickness of the N-side layer 11 is 6 μm, and the thickness ofthe P-side layer 13 is 0.1 μm. In addition, the inclined angle θe of theslope 16S is 500, the depth D at the portion occupied by the N-sidelayer 11 in the slope 16S is 1 μm, and the inclined angle θb of theN-side layer side surface 11S is 800.

FIG. 6(a) illustrates dependency of the light extraction efficiency onthe inclined angle θb of the N-side layer side surface 11S. In FIG.6(a), a horizontal axis indicates the inclined angle θb. As illustratedin FIG. 6(a), as the inclined angle θb of the N-side layer side surface11S becomes smaller, the light extraction efficiency is improved.Preferably, the inclined angle θb of the N-side layer side surface 11Sis equal to or less than 83°.

FIG. 6(b) illustrates dependency of the light extraction efficiency onthe depth D at the portion occupied by the N-side layer 11 in the slope16S. In FIG. 6(b), a horizontal axis indicates the depth D. Asillustrated in FIG. 6(b), as the depth D increases, the light extractionefficiency is improved. Preferably, the depth D is equal to or more than0.6 μm.

FIG. 6(c) illustrates dependency of the light extraction efficiency onthe inclined angle θe of the slope 16S. In FIG. 6(c), a horizontal axisindicates the inclined angle θe. In order to improve the lightextraction efficiency, the inclined angle θe is preferably equal to orless than 600, and further preferably equal to or less than 500. FIG.6(d) illustrates dependency of the light extraction efficiency on thethickness of the N-side layer 11. The thickness is a thickness in thevertical direction (direction from the upper surface of the micro lightemitting element 100 toward the lower surface). In FIG. 6(d), ahorizontal axis indicates the thickness of the N-side layer 11. As thethickness of the N-side layer 11 becomes thicker, the light extractionefficiency is improved. The thickness of the N-side layer 11 ispreferably equal to or more than 3 μm.

FIG. 6(e) illustrates dependency of the light extraction efficiency onthe thickness of the P-side layer 13. In FIG. 6(e), a horizontal axisindicates the thickness of the P-side layer 13. As the thickness of theP-side layer 13 becomes thicker, the light extraction efficiency isimproved. However, the influence is smaller than those of otherparameters illustrated in FIGS. 6(a) to 6(d).

With the drawings, the micro light emitting element 100 according to oneform of the present invention can realize light extraction efficiencywhich is equal to or more than at least 48%. This exhibits very largeimprovement of about 2.7 times the light extraction efficiency in therectangular parallelepiped structure, which is shown in Table 2.Further, in the micro light emitting element 100 according to the oneform of the present invention, it is possible to realize the lightextraction efficiency of 70% or more by appropriately selecting thestructure of the micro light emitting element 100.

In the micro light emitting element 100 according to the one form of thepresent invention, the entire periphery of the side surface of the lightemission layer 12 is configured as the portion of the slope 16S, and theN-side layer side surface 11S from the slope 16S to the upper surface ofthe N-side layer 11 is inclined by an angle larger than the angle of theslope 16S. In addition, in the micro light emitting element 100, theslope 16S and the N-side layer side surface 11S are covered by the metalreflective layer 20W.

Thus, it is possible to prevent the occurrence of optical crosstalkbetween the micro light emitting elements 100 and to significantlyimprove the light extraction efficiency. Further, since the transparentinsulating film 17 is disposed between the slope 16S and the N-sidelayer side surface 11S, and the metal reflective layer 20W, it ispossible to further improve the light extraction efficiency.

Embodiment 2

(Configuration of Image Display Element 200 a) Another embodiment of thepresent invention will be described below with reference to FIGS. 7 and8. For easy description, members having the same functions as themembers described in the above embodiment are denoted by the samereference signs, and repetitive descriptions thereof will not be made.An image display element 200 a in Embodiment 2 is different from theimage display element 200 in Embodiment 1 in that sticking between thedriving circuit substrate 50 and the micro light emitting element 100 ais performed in a manner of wafer-to-wafer bonding. The wafer-to-waferbonding has an advantage in that generation of dust is suppressed, andhigh yield is realized.

FIG. 7 is a schematic sectional view of the image display element 200 aaccording to Embodiment 2 of the present invention. Differing from themicro light emitting element 100, a micro light emitting element 100 ais buried by an insulating film 21, and a surface of the micro lightemitting element 100 a on an opposite side of the light emitting surfaceis flat. The micro light emitting element 100 a and the driving circuitsubstrate 50 are stuck to each other on a flat bonding surface. AP-damascene electrode 23P and an N-damascene electrode 23N in the microlight emitting element 100 a are bonded to the P-drive electrode 51 andthe N-drive electrode 52 on the driving circuit substrate 50,respectively.

As described later, the P-damascene electrode 23P and the N-damasceneelectrode 23N are formed by the same process. Thus, the P-damasceneelectrode and the N-damascene electrode are formed of the same wiringmaterial regardless of the different shape, size, and depth. That is,the P-damascene electrode 23P and the N-damascene electrode 23N have thesame stacked structure including a barrier metal layer, a mainconductive layer, a cap layer, and the like. Lower surfaces of theP-damascene electrode 23P and the N-damascene electrode 23N areconfigured in substantially the same plane as the lower surface of theinsulating film 21. The structure except for the above description issimilar to that of the image display element 200 in Embodiment 1.

The surface of the insulating film 55 (on the driving circuit substrate50 side) on the bonding surface side is also flat, and upper surfaces ofthe P-drive electrode 51 and the N-drive electrode 52 are configured insubstantially the same plane as the upper surface of the insulating film55. A slight difference in height may be provided between the lowersurface of the insulating film 21, and the lower surfaces of theP-damascene electrode 23P and the N-damascene electrode 23N, so long assticking of the micro light emitting element 100 a and the drivingcircuit substrate 50 is possible. This is similarly applied to adifference in height between the upper surface of the insulating film 55on the driving circuit substrate 50 side, and the upper surfaces of theP-drive electrode 51 and the N-drive electrode 52.

Normally, a layer constituting the lower surfaces of the P-damasceneelectrode 23P and the N-damascene electrode 23N has the same material asthat of a layer constituting the upper surfaces of the P-drive electrode51 and the N-drive electrode 52. Examples of the material of the abovelayers include gold (Au), copper (Cu), and nickel (Ni).

(Manufacturing Flow of Image Display Element 200 a)

FIGS. 8(a) to 8(d) are schematic sectional views illustrating amanufacturing flow of the image display element 200 a according toEmbodiment 2 of the present invention. In descriptions of themanufacturing flow of the image display element 200 a in FIGS. 8(a) to8(c), the insulating film 21 side is set to be upper, and the growthsubstrate 9 side is set to be lower. In descriptions of themanufacturing flow of the image display element 200 a in FIG. 8(d), thegrowth substrate 9 side is set to be upper, and the driving circuitsubstrate 50 side is set to be lower.

FIG. 8 illustrates only the pixel region 1 and the N connection region 3of an image display element 200 a, but the manufacturing flow of theimage display element 200 a is not performed for each image displayelement 200 a. In the manufacturing flow of the image display element200 a, preferably, a plurality of image display elements 200 a aremanufactured at a time by sticking a wafer for a plurality of drivingcircuit substrates 50 and a wafer for a plurality of micro lightemitting elements 100 a to each other.

A portion of the manufacturing flow of the micro light emitting element100 a is the same as the processes for the micro light emitting element100, which are illustrated in FIGS. 2(a) to 2(g). In the manufacturingflow of the micro light emitting element 100 a, after the metal layer 20is patterned as illustrated in FIG. 8(a), the insulating film 21 isdeposited to cover the exposed portions of the P-electrode 20P, thetransparent insulating film 17, and the metal reflective layer 20W.

After the insulating film 21 is deposited, the upper surface of theinsulating film 21 is flattened by a chemical-mechanical-polishing (CMP)method. The insulating film 21 is, for example, a film of SiO₂, SiN,SiON or a film obtained by stacking these film. Various film formationtechnologies such as a chemical vapor deposition (CVD) method, asputtering method, and a coating method can be used for forming theinsulating film 21.

After the insulating film 21 is flattened, as illustrated in FIG. 8(b),a P-trench 22P and an N-trench 22N are formed in the insulating film 21on the P-electrode 20P and the N-electrode 20N, respectively. TheP-trench 22P has a hole shape and reaches the P-electrode 20P. TheN-trench 22N has a hole shape or a line shape and reaches theN-electrode 20N.

After the P-trench 22P and the N-trench 22N are formed, as illustratedin FIG. 8(c), the P-damascene electrode 23P and the N-damasceneelectrode 23N are formed by burying a metal film in the P-trench 22P andthe N-trench 22N with a damascene method. The metal film is, forexample, a combination of copper and a barrier film of tantalum (Ta),tungsten (W), and titanium nitride (TiN). The metal film may be acombination of gold (Au), nickel (Ni) or the like with the correspondingbarrier film.

In the damascene method, a metal thin film is deposited on an underlyingstructure having a trench, and the metal thin film is polished by a CMPmethod. Thus, the metal thin film can remain in the trench, and theupper surface of the underlying structure is level with the uppersurface of the metal thin film. In the above-described manner, theP-damascene electrode 23P is disposed on the P-electrode 20P, and theN-damascene electrode 23N is disposed on the N-electrode 20N. TheP-damascene electrode 23P and the N-damascene electrode 23N areconfigured with the same material. The upper surface of each of theP-damascene electrode 23P and the N-damascene electrode 23N are levelwith the surface, which functions as the bonding surface to the drivingcircuit substrate 50.

After the P-damascene electrode 23P and the N-damascene electrode 23Nare formed, as illustrated in FIG. 8(d), the micro light emittingelement 100 a and the dummy connection element 101 a are stuck to thedriving circuit substrate 50. At this time, the P-damascene electrode23P and the N-damascene electrode 23N are precisely aligned to overlapwith the corresponding P-drive electrode 51 and N-drive electrode 52,respectively.

Two wafers are stuck to each other by plasma cleaning of the surface,activation by ion irradiation, heating, and pressurization, inaccordance with the material of the bonding surface between the microlight emitting element 100 a and the dummy connection element 101 a, andthe driving circuit substrate 50. In the subsequent processes, similarto the processes illustrated in FIGS. 3(c) to 3(e), the growth substrate9 is removed, and the common N-electrode 40 is formed. In themanufacturing flow of the micro light emitting element 100 a, since theinsulating film 21 is deposited between the micro light emittingelements 100 a, the filling material 60 is not required.

In the configuration of the image display element 200 a, the peripheryof the micro light emitting element 100 a is covered by the metalreflective layer 20W. Thus, even though the transparent insulating filmis deposited between the micro light emitting elements 100 a, theoccurrence of light leakage between the micro light emitting elements100 a adjacent to each other is prevented. Thus, even though aninsulating film such as SiO₂, which is generally used, is used, it ispossible to prevent an occurrence of a problem that contrast and colorpurity are degraded.

As described above, since the wafers are stuck to each other, it ispossible to reduce dust generation and to realize high yield. Forexample, if the micro light emitting elements are divided in a unit ofthe image display element, a large amount of dust is generated in thedivision process. Thus, a problem that the yield is significantlydecreased by the bonding occurs, because the dusts are adhered to thebonding surface in a process of sticking the micro light emittingelement to the driving circuit substrate.

If the micro light emitting element 100 a and the driving circuitsubstrate 50 are both in the wafer state, such a problem does not occur.In a case where the micro light emitting element and the driving circuitsubstrate are stuck to each other for each image display element, a timeof about 1 to several minutes is required for one sticking process.Thus, production efficiency is low. However, in the process of stickingthe wafers to each other, the plurality of micro light emitting elements100 a serving as one wafer and the plurality of driving circuitsubstrates 50 serving as one wafer are bonded to each other at a time.Thus, it is possible to largely improve the production efficiency.

Preferably, the material of the wafer for the plurality of micro lightemitting elements 100 a is the same as the material of the wafer for theplurality of driving circuit substrates 50. The reason is as follows.That is, in sticking of the wafers, heating may be required. If thematerials of both the wafers are the same as each other, it is possibleto suppress a shift of a pattern occurring by a difference in thermalexpansion coefficient. Further, preferably, the sizes of both the wafersare equal to each other. The reason is that, if the sizes of both thewafers are not equal to each other, a wasteful region which is not usedis appeared on the larger wafer side.

As described above, similar to Embodiment 1, in the configuration of theimage display element 200 a, it is also possible to improve the lightextraction efficiency by the metal reflective layer 20W and to preventthe occurrence of light leakage between the micro light emittingelements 100 a adjacent to each other. Further, it is possible tofurther improve the light extraction efficiency by the transparentinsulating film 17.

Embodiment 3

(Configuration of Image Display Element 200 b)

Still another embodiment of the present invention will be describedbelow with reference to FIGS. 9 and 10. For easy description, membershaving the same functions as the members described in the aboveembodiment are denoted by the same reference signs, and repetitivedescriptions thereof will not be made. An image display element 200 b inEmbodiment 3 is different from the image display element 200 a inEmbodiment 2 in that the P-electrode 20P and the N-electrode 20N are notprovided, and the P-damascene electrode 23P and the N-damasceneelectrode 23N are directly connected to the P-side metal layer 10 of themicro light emitting element 100 b and the N-side layer 11 of a dummyconnection element 101 b, respectively. The image display element 200 bis the same as the image display element 200 a except for the abovepoints.

FIG. 9(a) is a schematic sectional view of an image display element 200b according to Embodiment 3 of the present invention. FIG. 9(b) is aschematic plan view of a micro light emitting element 100 b according toEmbodiment 3 of the present invention. In the configuration of the imagedisplay element 200 b, it is possible to omit the process of forming theP-contact hole 19P and the N-contact hole 19N, and thus it is possibleto reduce the processes in comparison to the image display element 200 ain Embodiment 2.

Further, as illustrated in FIG. 9(b), it is easy to form an elongatedrectangular micro light emitting element 100 b. In the image displayelement 200 a in Embodiment 2, since the metal reflective layer 20W andthe P-electrode 20P are processed by the same photolithographic process,it is necessary to secure a space having at least the minimum line widthbetween the metal reflective layer 20W and the P-electrode 20P.Therefore, the width of the P-electrode 20P is to be narrow.

Thus, if the width of the P-side metal layer 10 is narrow, it isdifficult to secure an installation area for the P-electrode 20P.However, in the configuration of the image display element 200 b, theP-damascene electrode 23P may be formed not to come into contact withthe metal reflective layer 20W, and a space necessary for alignment maybe secured. Thus, the configuration of the image display element 200 bcan be applied to a case where the P-side metal layer 10 is narrowerthan that in the configuration of the image display element 200 a.

(Manufacturing Flow of Image Display Element 200 b)

FIGS. 10(a) to 10(g) are schematic sectional views illustrating amanufacturing flow of the image display element 200 b according toEmbodiment 3 of the present invention. In descriptions of themanufacturing flow of the image display element 200 b in FIGS. 10(a) to10(e), the metal layer 20 side is set to be upper, and the growthsubstrate 9 side is set to be lower. In the manufacturing flow of theimage display element 200 b, the processes illustrated in FIGS. 2(a) to2(d) are performed, and then, as illustrated in FIG. 10(a), the metallayer 20 is deposit without forming the P-contact hole 19P.

After the metal layer 20 is deposited, as illustrated in FIG. 10(b), themetal layer 20 is processed to obtain the metal reflective layer 20W. Atthis time, portions of the metal layer 20, which are above the P-sidemetal layer 10 and the N-contact trench 15N are removed. Then, asillustrated in FIG. 10(c), the insulating film 21 is deposited to coverexposed portions of the transparent insulating film 17 and the metalreflective layer 20W. The upper surface of the insulating film 21 isflattened by the CMP method.

After the upper surface of the insulating film 21 is flattened, asillustrated in FIG. 10(d), the P-trench 22P is formed on the P-sidemetal layer 10 in the pixel region 1, and the N-trench 22N is formed onthe N-contact trench 15N in the N connection region 3. Specifically, theP-trench 22P is formed by removing the insulating film 21 and thetransparent insulating film 17 on the P-side metal layer 10. TheN-trench 22N is formed by removing the insulating film 21 and thetransparent insulating film 17 on the N-side layer 11 in the N-contacttrench 15N.

Further, as illustrated in FIG. 10(e), the P-damascene electrode 23P isformed in the P-trench 22P, and the N-damascene electrode 23N is formedin the N-trench 22N. After the P-damascene electrode 23P and theN-damascene electrode 23N are formed, as illustrated in FIG. 10(f), theplurality of micro light emitting elements 100 b and the driving circuitsubstrate 50 are stuck to each other. Then, as illustrated in FIG.10(g), the growth substrate 9 is removed, and the common N-electrode 40is deposited to cover the exposed portions of the N-side layer 11, thetransparent insulating film 17, the metal reflective layer 20W, and thefilling material 60.

As described above, similar to Embodiment 1, in the configuration of theimage display element 200 b, it is also possible to improve the lightextraction efficiency by the metal reflective layer 20W and to preventthe occurrence of light leakage between the micro light emittingelements 100 b adjacent to each other. As described above, similar tothe image display element 200 a in Embodiment 2, in the configuration ofthe image display element 200 b, since the wafers are stuck to eachother, it is possible to improve productivity, to reduce the dustgeneration, and to realize high yield.

Embodiment 4

(Configuration of Image Display Element 200 c)

Still another embodiment of the present invention will be describedbelow with reference to FIGS. 11 and 12. For easy description, membershaving the same functions as the members described in the aboveembodiment are denoted by the same reference signs, and repetitivedescriptions thereof will not be made. An image display element 200 c inEmbodiment 4 is different from the image display element 200 inEmbodiment 1 in that a micro light emitting element 100 c includes theP-electrode 20P and the N-electrode 20N on the lower surface of themicro light emitting element. In FIG. 11, the image display element 200c is not filled with the filling material 60. However, similar toEmbodiment 1, the image display element may be filled with the fillingmaterial 60.

In addition, the image display element 200 c is different from the imagedisplay element 200 in that a driving circuit substrate 50 c includesthe N-drive electrode 52 in the pixel region 1, and there is a portionat which the transparent insulating film 17 is not provided between themetal reflective layer 20W and the N-side layer side surface 11S. Theimage display element 200 c is the same as the image display element 200except for the above points.

FIG. 11 is a schematic sectional view of the pixel region 1 in the imagedisplay element 200 c according to Embodiment 4 of the presentinvention. The configuration of the image display element 200 c has anadditional advantage in that, after the micro light emitting element 100c is stuck to the driving circuit substrate 50 c, it is not necessary toform the common N-electrode. In the configuration of the image displayelement 200 c, as illustrated in FIG. 11, the metal reflective layer 20Wis also used as the N-electrode (second electrode) 20N.

That is, the micro light emitting element 100 c includes the N-electrode20N which is electrically connected to the metal reflective layer 20W,on a surface on an opposite side of the light emitting surface side. TheP-electrode 20P and the N-electrode 20N for supplying a current to themicro light emitting elements 100 c are arranged in a two-dimensionalarray shape on the surface of the pixel region 1 in the driving circuitsubstrate 50 c.

The driving circuit substrate 50 c includes the P-drive electrode 51(connected to the P-electrode 20P of each micro light emitting element100 c through the bonding material 70) and the N-drive electrode 52(connected to the metal reflective layer 20W also used as theN-electrode 20N, through the bonding material 70) in the pixel region 1.In FIG. 11, N-electrodes 20N of two micro light emitting elements 100 cadjacent to each other are connected to one N-drive electrode 52.

(Manufacturing Flow of Image Display Element 200 c)

FIGS. 12(a) to 12(f) are schematic sectional views illustrating amanufacturing flow of the image display element 200 c according toEmbodiment 4 of the present invention. In descriptions of themanufacturing flow of the image display element 200 c in FIGS. 12(a) to12(d), the transparent insulating film 17 side is set to be upper, andthe growth substrate 9 side is set to be lower. In descriptions of themanufacturing flow of the image display element 200 c in FIGS. 12(e) and12(f), the growth substrate 9 side is set to be upper, and the drivingcircuit substrate 50 c side is set to be lower.

In the manufacturing flow of the image display element 200 c, the stateof the image display element 200 c (illustrated in FIG. 12(a)) isconsidered to be after the processes illustrated in FIGS. 2(a) to 2(d)are performed. In this state, as illustrated in FIG. 12(b), theP-contact hole 19P is formed on the P-side metal layer 10. A bottomopening 19BN of the N-side layer 11 is formed at a portion of the N-sidelayer side surface 11S.

In FIG. 12(b), a portion of the transparent insulating film 17 providedon the N-side layer side surface 11S is removed to expose the N-sidelayer side surface 11S for the two adjacent N-side layer side surfaces11S facing to each other. In the configuration of the image displayelement 200 c, the N-side layer side surface 11S is inclined. Thus, itis possible to etch the transparent insulating film 17 even by a dryetching method.

Accordingly, it is possible to adjust dimensions of the bottom opening19BN with high precision, and to reduce the removed portion of thetransparent insulating film 17 to be the necessary minimum. In a casewhere the N-side layer side surface 11S has no taper and isperpendicular to the growth substrate 9, wet etching has to be used, andcontrollability of dimensions in pattern is low.

Then, after the P-contact hole 19P and the bottom opening 19BN areformed, as illustrated in FIG. 12(c), the metal layer 20 is deposited tocover exposed portions of the growth substrate 9, the P-side metal layer10, the N-side layer 11, and the transparent insulating film 17.Further, as illustrated in FIG. 12(d), the metal layer 20 is processedwith a photolithographic method and an anisotropic dry etching method.Since the metal layer 20 is processed in this manner, the P-electrode20P is formed on the P-contact hole 19P, and the metal reflective layer20W is formed to cover a portion of the transparent insulating film 17on the slope 16S and the N-side layer side surface 11S. The metalreflective layer 20W is in electrical contact with the N-side layer 11in the bottom opening 19BN.

After the metal layer 20 is processed, as illustrated in FIG. 12(e), themicro light emitting element 100 c and the driving circuit substrate 50c are stuck to each other with the bonding material 70. After the microlight emitting element 100 c and the driving circuit substrate 50 c arestuck to each other, as illustrated in FIG. 12(f), the growth substrate9 is removed. Then, similar to other embodiments, a space between microlight emitting elements 100 c may be filled with a filling material.

In the configuration of the image display element 200 c, a portion atwhich the transparent insulating film 17 is not provided between themetal reflective layer 20W and the N-side layer side surface 11S isprovided among portions of the N-side layer side surface 11S. That is,the metal reflective layer 20W is electrically connected to the N-sidelayer 11, and more specifically, is electrically connected to at least aportion of the N-side layer side surface 11S.

When a structure obtained by removing the transparent insulating film 17on an entire surface of one of four the N-side layer side surfaces 11Sis simulated, the decrease rate of the light extraction efficiency isequal to or less than 3% in comparison to a case where the entiresurface of the N-side layer side surface 11S is covered by thetransparent insulating film 17. Thus, the light extraction efficiency bythe configuration of the image display element 200 c has an advantageover the structure in the related art.

As described above, similar to Embodiment 1, it is also possible toimprove the light extraction efficiency and to prevent the occurrence oflight leakage between the micro light emitting elements 100 c adjacentto each other. Furthermore the configuration of the image displayelement 200 c has an additional advantage in that it is not necessary toform the common N-electrode 40 after the micro light emitting element100 c and the driving circuit substrate 50 c are stuck to each other,and the growth substrate 9 is removed.

Embodiment 5

(Configuration of Image Display Element 200 d)

Still another embodiment of the present invention will be describedbelow with reference to FIGS. 13 to 15. For easy description, membershaving the same functions as the members described in the aboveembodiment are denoted by the same reference signs, and repetitivedescriptions thereof will not be made. An image display element 200 d inEmbodiment 5 is different from the image display element 200 c inEmbodiment 4 in that the transparent insulating film 17 is disposed onlyfor the slope 16S among the slope 16S and the N-side layer side surface11S.

In addition, the image display element 200 d is different from the imagedisplay element 200 c in that the metal reflective layer 20W(N-electrode 20N) of one micro light emitting element 100 c is connectedto one N-drive electrode 52. The image display element 200 d is the sameas the image display element 200 c except for the above points.

Thus, since the N-side layer side surface 11S is covered by the metalreflective layer 20W, it is possible to prevent the occurrence ofoptical crosstalk. With the inclination of the slope 16S and the N-sidelayer side surface 11S, it is possible to realize light extractionefficiency higher than that in the rectangular parallelepiped structure.For example, in comparison to the light extraction efficiency of 17.9%in the rectangular parallelepiped structure shown in Table 2, in theconfiguration of the image display element 200 d, it is possible torealize the light extraction efficiency of 67.8% being about 3.8 timesthe light extraction efficiency in the rectangular parallelepipedstructure. Further, manufacturing of the image display element 200 d iseasier than manufacturing of the image display element 200 c inEmbodiment 4.

FIG. 13 is a schematic sectional view of the pixel region 1 in the imagedisplay element 200 d according to Embodiment 5 of the presentinvention. As illustrated in FIG. 13, a micro light emitting element 100d includes the P-electrode 20P and the N-electrode 20N on the lowersurface thereof. A driving circuit substrate 50 d includes the P-driveelectrode 51 and the N-drive electrode 52 on the micro light emittingelement 100 d side. The P-drive electrode 51 and the N-drive electrode52 have a relation with the P-electrode 20P and the N-electrode 20N inone-to-one correspondence. Similar to the image display element 200 c,the configuration of the image display element 200 d has an additionaladvantage in that, it is not necessary to form the common N-electrodeafter the micro light emitting element 100 d is stuck to the drivingcircuit substrate 50 d, and the growth substrate 9 is removed.

(Manufacturing Flow of Image Display Element 200 d)

FIGS. 14(a) to 14(e) are schematic sectional views illustrating themanufacturing flow of the image display element 200 d according toEmbodiment 5 of the present invention. In descriptions of themanufacturing flow of the image display element 200 d in FIGS. 14(a) to14(e), the transparent insulating film 17 side is set to be upper, andthe growth substrate 9 side is set to be lower. In the manufacturingflow of the image display element 200 d, after the separation trench 15is formed by performing the processes in FIGS. 2(a) and 2(b), asillustrated in FIG. 14(a), the transparent insulating film 17 isdeposited to cover exposed portions of the N-side layer 11, the lightemission layer 12, the P-side layer 13, and the P-side metal layer 10.

After the transparent insulating film 17 is deposited, as illustrated inFIG. 14(b), the isolation trench 18 is formed by etching the transparentinsulating film 17 and the N-side layer 11 on the bottom of theseparation trench 15. Preferably, the isolation trench 18 reaches thegrowth substrate 9 to separately divide micro light emitting elements100 d. The surface of the N-side layer 11, which is exposed at thisstage is the N-side layer side surface 11S. It is necessary that theinclined angle of the isolation trench 18, that is, the inclined angleθb of the N-side layer side surface 11S is about 80°, similar to FIG.2(c).

After the isolation trench 18 is formed, as illustrated in FIG. 14(c),the P-contact hole 19P is formed on the P-side metal layer 10. In aprocess of forming the P-contact hole 19P, it is not necessary to formthe bottom opening in the transparent insulating film 17 on the N-sidelayer side surface 11S as in FIG. 12(b) in Embodiment 4. Thus,manufacturing of the image display element 200 d is easier thanmanufacturing of the image display element 200 c.

After the P-contact hole 19P is formed, as illustrated in FIG. 14(d),the metal layer 20 is deposited to cover exposed portions of the growthsubstrate 9, the P-side metal layer 10, the N-side layer 11, and thetransparent insulating film 17. The metal layer 20 is in electricalcontact with the P-side metal layer 10 in the P-contact hole 19P and isin electrical contact with the N-side layer 11 on the N-side layer sidesurface 11S.

Further, as illustrated in FIG. 14(e), the metal layer 20 around aportion as the P-electrode 20P is removed, and thus the metal layer 20is divided into the P-electrode 20P and the metal reflective layer 20W.The metal reflective layer 20W is also used as the N-electrode 20N. Inthis manner, each micro light emitting element 100 d includes theP-electrode 20P and the N-electrode 20N. The subsequent processes willbe omitted because of being similar to those for the image displayelement 200 c in Embodiment 4. In FIG. 14(e), the metal layer 20 on thegrowth substrate 9 is also removed, but the metal portion can be removedlater at the growth substrate removal of FIGS. 12(e) and (f).

FIG. 15 illustrates results obtained by examining the change of thelight extraction efficiency to the dimensions and the angles of eachunit in the micro light emitting element 100 d with the simulationdescribed in Embodiment 1. FIGS. 15(a) to 15(e) are diagramsillustrating simulation results of dependency of the light extractionefficiency on dimensions and angles of each unit in the image displayelement 200 d illustrated in FIG. 13. FIGS. 15(a) to 15(f) alsoillustrate ratios (area ratio) of the area of the light emission layer12 to the area of the light emitting surface (upper surface of theN-side layer 11). In FIGS. 15(a) to 15(e), a vertical axis indicates thelight extraction efficiency or the area ratio.

In all cases in FIGS. 15(a) to 15(f), so long as particular statementsare not made, the size of the upper surface of the N-side layer 11 is 8μm×8 μm, the thickness of the N-side layer 11 is 6 μm, and the thicknessof the P-side layer 13 is 0.2 μm. In addition, the inclined angle θe ofthe slope 16S is 45°, the depth D at the portion occupied by the N-sidelayer 11 in the slope 16S is 1 μm, and the inclined angle θb of theN-side layer side surface 11S is 800. Further, the film thickness of thetransparent insulating film 17 is 400 nm.

FIG. 15(a) illustrates dependency of the light extraction efficiency onthe inclined angle θb of the N-side layer side surface 11S. In FIG.15(a), a horizontal axis indicates the inclined angle θb. As illustratedin FIG. 15(a), as the inclined angle θb of the N-side layer side surface11S becomes smaller, the light extraction efficiency is improved. In acase where the inclined angle θb is equal to or less than 900, the lightextraction efficiency is equal to or larger than 40%. Thus, it ispossible to realize the light extraction efficiency being two times thelight extraction efficiency of 17.9% in the rectangular parallelepipedstructure. Further, in a case where the inclined angle θb is equal to orless than 830, it is possible to realize the light extraction efficiencyof 60% or more.

FIG. 15(b) illustrates dependency of the light extraction efficiency onthe depth D at the portion occupied by the N-side layer 11 in the slope16S. In FIG. 15(b), a horizontal axis indicates the depth D. Asillustrated in FIG. 15(b), as the depth D increases, the lightextraction efficiency is improved. Since the depth D is equal to orgreater than 0.5 μm, it is possible to realize the light extractionefficiency of 60% or more.

FIG. 15(c) illustrates dependency of the light extraction efficiency onthe inclined angle θe of the slope 16S. In FIG. 15(c), a horizontal axisindicates the inclined angle θe. In order to improve the lightextraction efficiency, it is preferable that the inclined angle θe isequal to or less than 600. Thus, it is possible to realize the lightextraction efficiency of 60% or more. Further preferably, the inclinedangle θe is equal to or less than 500.

FIG. 15(d) illustrates dependency of the light extraction efficiency onthe thickness of the N-side layer 11. The thickness is a thickness inthe vertical direction (direction from the upper surface of the microlight emitting element 100 d toward the lower surface). In FIG. 15(d), ahorizontal axis indicates the thickness of the N-side layer 11. As thethickness of the N-side layer 11 becomes thicker, the light extractionefficiency is improved. It is preferable that the thickness of theN-side layer 11 is equal to or more than 3 μm, and thus it is possibleto realize the light extraction efficiency of 60% or more.

FIG. 15(e) illustrates dependency of the light extraction efficiency onthe thickness of the P-side layer 13. In FIG. 15(e), a horizontal axisindicates the thickness of the P-side layer 13. As the thickness of theP-side layer 13 becomes thicker, the light extraction efficiency isimproved. However, the influence is smaller than those of otherparameters illustrated in FIGS. 15(a) to 15(d).

FIG. 15(f) illustrates dependency of the light extraction efficiency onthe film thickness of the transparent insulating film 17. In FIG. 15(f),a vertical axis and a horizontal axis indicate the light extractionefficiency and film thickness of the transparent insulating film 17,respectively. As the film thickness of the transparent insulating film17 becomes thicker, the light extraction efficiency is improved.However, a change at the film thickness of 400 nm or more is small.Thus, it is most preferable that the film thickness of the transparentinsulating film 17 is equal to or more than 400 nm. The film thicknessof the transparent insulating film 17 may be equal to or more than atleast 75 nm such that the decrease of the light extraction efficiency iswithin 2% even in a case of the film thickness being 75 nm or more, incomparison to a case of the film thickness being 400 nm or more.

As illustrated in FIGS. 15(a) to 15(f), in the configuration of theimage display element 200 d, it is possible to realize the lightextraction efficiency of at least 40% or more. This is the lightextraction efficiency of 2.2 times the light extraction efficiency of17.9% in the rectangular parallelepiped structure shown in Table 2 andexhibits very large improvement of the light extraction efficiency.Further, in the configuration of the image display element 200 d, it ispossible to realize the light extraction efficiency of 60% or more byappropriately selecting the structure of the micro light emittingelement 100 d.

Embodiment 6

(Configuration of Image Display Element 200 e)

Still another embodiment of the present invention will be describedbelow with reference to FIG. 16. For easy description, members havingthe same functions as the members described in the above embodiment aredenoted by the same reference signs, and repetitive descriptions thereofwill not be made. An image display element 200 e in Embodiment 6 isdifferent from the image display element 200 in Embodiment 1 in that theP-side metal layer 10 is changed to a P-side metal layer (first metalfilm) 10 e. The image display element 200 e is the same as the imagedisplay element 200 except for the above points.

In the configuration of the image display element 200 e, a P-sidetransparent insulation film (P-side transparent insulation layer) (thirdtransparent insulating film) 25 is disposed between the P-side layer 13and the P-side metal layer 10 e. In addition, a P-side metal layercontact hole 26 is formed in the P-side transparent insulation film 25.Thus, the P-side layer 13 and the P-side metal layer 10 e areelectrically connected to each other.

As clear from the above descriptions, since the transparent insulatingfilm 17 is disposed between the metal reflective layer 20W and thecompound semiconductor 14, it is possible to improve reflectivity and toimprove the light extraction efficiency. However, if the P-side layer 13and the P-side metal layer 10 e are electrically connected to eachother, it is not possible to dispose a transparent insulating film onthe entire surface of the P-side layer 13. Therefore, the P-side metallayer contact hole 26 is formed to partially connect the P-side layer 13and the P-side metal layer 10 e to each other, and thus it is possibleto further improve the light extraction efficiency while the P-sidelayer 13 and the P-side metal layer 10 e are electrically connected.

(Manufacturing Flow of Image Display Element 200 e)

FIGS. 16(a) to 16(d) are schematic sectional views illustrating amanufacturing flow of the image display element 200 e according toEmbodiment 6 of the present invention. In descriptions of themanufacturing flow of the image display element 200 e, the P-side layer13 side is set to be upper, and the growth substrate 9 side is set to belower. In the manufacturing flow of the image display element 200 e,only a process of forming the P-side metal layer 10 e is explained here.Description about the processes other than the process of forming theP-side metal layer 10 e will be omitted, because processes described inother embodiments can be applied.

FIG. 16(a) illustrates a state where the compound semiconductor 14 isdeposited on the growth substrate 9. The sheet resistance of the P-sidelayer 13 in the image display element 200 e is preferably as low aspossible. The thickness of the P-side layer 13 in the image displayelement 200 e may be thicker than the thickness of the P-side layer 13described in Embodiments 1 to 5.

Then, as illustrated in FIG. 16(b), the P-side transparent insulationfilm 25 is deposited on the P-side layer 13. The material and thethickness of the P-side transparent insulation film 25 may be the sameas the material and the thickness of the transparent insulating film 17.After the P-side transparent insulation film 25 is deposited, asillustrated in FIG. 16(c), the P-side metal layer contact hole 26 isformed in the upper surface of the P-side transparent insulation film25. The P-side metal layer contact hole 26 extends from the P-sidetransparent insulation film 25 to the P-side layer 13.

Preferably, a ratio of an area occupied by the P-side metal layercontact hole 26 in the upper surface of the P-side transparentinsulation film 25 is small. For example, if P-side metal layer contactholes 26 having a diameter of 0.1 μm are formed at a pitch of 1 μm, theratio of the area occupied by the P-side metal layer contact holes 26 inthe upper surface of the P-side transparent insulation film 25 is about1/100. In this case, even if the P-side metal layer contact hole 26 isfilled with a metal layer, it is possible to sufficiently maintain thelight extraction efficiency by the P-side transparent insulation film25.

The ratio of the area occupied by the P-side metal layer contact holes26 in the upper surface of the P-side transparent insulation film 25 issmaller, then the effect of improving the light extraction efficiency islarger. However, for example, even if the P-side metal layer contacthole 26 occupies about half of an area of the upper surface of theP-side transparent insulation film 25, it is possible to sufficientlymaintain improvement effect at the light extraction efficiency.

After the P-side metal layer contact hole 26 is formed, as illustratedin FIG. 16(d), the P-side metal layer 10 e is deposited to cover exposedportions of the P-side transparent insulation film 25 and the P-sidelayer 13. At this time, the P-side metal layer contact hole 26 is filledwith a metal material such as palladium (Pd), which is easy to obtain anohmic contact with the P-side layer 13, and a metal layer of silver oraluminum having high visible light reflectivity may be deposited on themetal material.

Regarding the structure and the manufacturing method of the micro lightemitting element and the image display element 200 e to apply this form,a combination with any form of Embodiments 1 to 5 may be made. Thus,descriptions thereof will be omitted. If any form of Embodiments 1 to 5is combined with Embodiment 6, it is possible to further enhance theeffect of improving the light extraction efficiency, which is providedin any form of Embodiments 1 to 5. And also the P-side metal layer 10 eprevents downward emission of light like the P-side metal layer 10 ofEmbodiments 1.

In the following Table 3, a case where the P-side transparent insulationfilm is added to Embodiment 1 structure is compared with a case ofEmbodiment 1 without the P-side transparent insulation film. With theconfiguration obtained by combining the configuration in Embodiment 6 tothe configuration in Embodiment 1, it is possible to reduce theabsorption amount of the lower surface and to improve the lightextraction efficiency to be about 4%. Table 3 shows simulation resultsof the light extraction efficiency.

TABLE 3 P-side transparent insulation film None Provided Lightextraction efficiency 80.7% 84.9% Side surface absorption 8.8% 9.2%Bottom surface absorption 6.0% 0.8% Internal absorption 4.5% 5.1%Average internal reflection number 25.4 26.3

If any form of Embodiments 1 to 5 is combined with Embodiment 6, it ispossible to further enhance the effect of improving the light extractionefficiency, which is provided in any form of Embodiments 1 to 5. And itis also possible to prevent the occurrence of light leakage between themicro light emitting elements 100 e adjacent to each other.

Embodiment 7

(Configuration of Image Display Element 200 f)

Still another embodiment of the present invention will be describedbelow with reference to FIG. 17. For easy description, members havingthe same functions as the members described in the above embodiment aredenoted by the same reference signs, and repetitive descriptions thereofwill not be made. An image display element 200 f in Embodiment 7 isdifferent from the image display element 200 e in Embodiment 6 in viewof a method of electrically connecting the P-side layer 13 and a P-sidemetal layer (first metal film) 10 f. The image display element 200 f isthe same as the image display element 200 e except for the electricalconnection method.

In the configuration of the image display element 200 f, the P-sidelayer 13 is deposited to be thicker than the P-side layer 13 in theimage display element 200 e. Anisotropic etching is performed on theP-side layer 13 to form a pillar shape. Thus, a P-side layer pillar 27is formed. A P-side transparent insulation film (second transparentinsulating film) 25 f buries the P-side layer pillars 27, and the P-sidemetal layer 10 f being a metal layer is deposited on the P-sidetransparent insulation film 25 f.

(Manufacturing Flow of Image Display Element 200 f)

FIGS. 17(a) to 17(d) are schematic sectional views illustrating amanufacturing flow of the image display element 200 f according toEmbodiment 7 of the present invention. In descriptions of themanufacturing flow of the image display element 200 f, the P-side layer13 side is set to be upper, and the growth substrate 9 side is set to belower. In the manufacturing flow of the image display element 200 f, asillustrated in FIG. 17(a), the compound semiconductor 14 is deposited onthe growth substrate 9. The thickness of the P-side layer 13 is equal toor more than at least 100 nm.

After the compound semiconductor 14 is deposited, as illustrated in FIG.17(b), the P-side layer 13 is etched by the photolithographic method andthe anisotropic etching method, so as to remain the bottom of the P-sidelayer 13 and the P-side layer pillar 27. The height of the P-side layerpillar 27 is 25 nm to 1 μm. In plan view from the light emitting surfaceside, a ratio of the total area for upper surfaces of a plurality ofP-side layer pillars 27 to the area of the horizontal surface of theP-side metal layer 10 f is preferably small. However, even though theratio is about 50%, the effect of improving the light extractionefficiency is obtained.

After the P-side layer 13 is etched, as illustrated in FIG. 17(c), theP-side transparent insulation film 25 f is deposited between the P-sidelayer pillars 27, and an upper portion of the P-side layer pillar 27 isexposed. For example, after the P-side transparent insulation film 25 fis deposited, the P-side transparent insulation film 25 f is polished bythe CMP method, and thus it is possible to expose the upper portion ofthe P-side layer pillar 27.

A metal film may be formed in advance, on the upper surface of theP-side layer pillar 27. For example, metal such as palladium may bedeposited on the upper surface of the P-side layer 13, and the P-sidelayer 13 may be processed to process the metal and to form the P-sidelayer pillar 27. Thus, the metal can be caused to function as a stopperlayer for stopping polishing by the CMP method, and it is possible torealize ohmic contact between the P-side layer 13 and the metal.

Further, without using the photolithographic method, metal nanoparticlemay be dispersed and arranged on the upper surface of the P-side layer13, and the P-side layer 13 may be subjected to anisotropic etching byusing the arranged metal nanoparticles as a mask layer. If the metalnanoparticles have a diameter of several tens of nanometers, even thoughthe anisotropic etching is not necessarily performed on the P-side layer13, it is possible to obtain the effect of improving the lightextraction efficiency only by burying the P-side transparent insulationfilm 25 f between the metal nanoparticles. After the P-side transparentinsulation film 25 f is deposited, as illustrated in FIG. 17(d), theP-side metal layer 10 f is deposited on the P-side layer pillar 27 andthe P-side transparent insulation film 25 f. The P-side metal layer 10 fprevents downward emission of light just like the P-side metal layer 10of Embodiments 1.

Regarding the structure and the manufacturing method of the micro lightemitting element and the image display element 200 f to apply this form,a combination with any form of Embodiments 1 to 5 may be made. Thus,descriptions thereof will be omitted. If any form of Embodiments 1 to 5is combined with Embodiment 7, it is possible to further enhance theeffect of improving the light extraction efficiency, which is providedin any form of Embodiments 1 to 5. And it is also possible to preventthe occurrence of light leakage between the micro light emittingelements 100 f adjacent to each other.

Embodiment 8

(Configuration of Image Display Element 200 g)

Still another embodiment of the present invention will be describedbelow with reference to FIG. 18. For easy description, members havingthe same functions as the members described in the above embodiment aredenoted by the same reference signs, and repetitive descriptions thereofwill not be made.

An image display element 200 g in Embodiment 8 is different from theimage display element 200 in Embodiment 1 in that the inclined angle θeof the slope 16S is substantially equal to the inclined angle θb of theN-side layer side surface 11S. The image display element 200 g is thesame as the image display element 200 except for the above point. Sincethe inclined angle θe of the slope 16S is substantially equal to theinclined angle θb of the N-side layer side surface 11S, the slope 16Sextends to the light emitting surface. At this time, the slope 16S iscovered by the metal reflective layer 20W, and the transparentinsulating film 17 is disposed between the slope 16S and the metalreflective layer 20W.

FIG. 18(a) is an aerial view of a micro light emitting element having atruncated pyramid type structure according to Embodiment 8 of thepresent invention. FIG. 18(b) is a diagram illustrating a simulationresult of dependency of the light extraction efficiency on the inclinedangle. FIG. 18(c) is a diagram illustrating a simulation result of filmthickness dependency of the transparent insulating film in the lightextraction efficiency.

As illustrated in FIG. 18(a), the shape of a micro light emittingelement 100 g in the image display element 200 g is a truncated pyramidtype. In the manufacturing flow of the image display element 200 g, anisolation trench may be formed by combining the processes illustrated inFIGS. 2(b) and 2(c) to one process, such that the inclined angle θe issubstantially equal to the inclined angle θb.

(Manufacturing Flow of Image Display Element 200 g)

In the manufacturing flow of the image display element 200 g, processesother than a process of forming the isolation trench are similar tothose in the manufacturing flow of the image display element 200 inEmbodiment 1. In the manufacturing flow of the image display element 200g, it is possible to reduce the manufacturing flow by one process.Generally, in comparison to the image display element 200, since theinclined angle θb of the N-side layer side surface 11S is small, it ispossible to more easily deposit the metal layer 20 on the transparentinsulating film 17 deposited on the N-side layer side surface 11S.

In the following Table 4, light emission characteristics of the microlight emitting element having the rectangular parallelepiped structurewas compared with light emission characteristics of the micro lightemitting element 100 g having the truncated pyramid type. In all of acase of the micro light emitting element having the rectangularparallelepiped structure and a case of the micro light emitting element100 g, the size of the upper surface of the N-side layer 11 was 8 m×8μm, and the same compound semiconductor was used. In the case of themicro light emitting element having the rectangular parallelepipedstructure and the case of the micro light emitting element 100 g, theconstituent materials and the formation processes are the same as eachother except for a different shape.

In the case of the micro light emitting element having the rectangularparallelepiped structure, the separation trench and the isolation trenchwere processed to be inclined as small as possible. In addition, in thecase of the micro light emitting element 100 g, the side surface of theN-side layer 11, which was formed by the isolation trench 18 wasprocessed and formed such that inclined angles θe and θb were about 80°.In all cases, the transparent resin layer was disposed on the uppersurface of the N-side layer 11. In all cases, 10000 pieces of microlight emitting elements in 100 rows×100 columns simultaneously turned onto evaluate the total luminous flux intensity. The current amount perone micro light emitting element 100 g is 5 μA. The following Table 4shows measurement results.

TABLE 4 Rectangular Truncated bent parallelepiped pyramid structure typestructure External quantum efficiency 12% 32% Area ratio of lightemission layer 100%  54% to light emitting surface Estimated effectiveinternal 66% 60% quantum efficiency

As shown in Table 4, in the micro light emitting element 100 g havingthe truncated pyramid type, the external quantum efficiency of about 2.7times that in the micro light emitting element having the simplerectangular parallelepiped structure is obtained. Table 5 shows resultsobtained by simulating the light extraction efficiency with the laytrace method. Estimated effective internal quantum efficiency shown inTable 4 is an estimated value obtained by being calculated from theexternal quantum efficiency shown in Table 4 with the light extractionefficiency shown in Table 5. In the micro light emitting element 100 ghaving the truncated pyramid type, the light extraction efficiency ofabout 3.0 times that in the micro light emitting element having thesimple rectangular parallelepiped structure is obtained. Values shown inTable 5 are simulation values.

TABLE 5 Rectangular Truncated bent parallelepiped pyramid structure typestructure Light extraction efficiency 17.9% 53.7% Side surfaceabsorption 29.4% 23.0% Bottom surface absorption 29.5% 12.1% Internalabsorption 23.2% 11.2% Average internal reflection 85.4 40.1 number

As illustrated in FIG. 18(b), as the inclined angle θb becomes smaller,the light extraction efficiency is improved. In a case where theinclined angle θb is equal to or less than 82°, it is possible torealize the light extraction efficiency of 48% or more. Further, in acase where the inclined angle θb is equal to or less than 75°, it ispossible to realize the light extraction efficiency of 70% or more.

As illustrated in FIG. 18(c), when the film thickness of the transparentinsulating film 17 is equal to or more than 75 nm, it is possible torealize the light extraction efficiency of 48% or more. In FIG. 18(c), avertical axis indicates the light extraction efficiency, and ahorizontal axis indicates the film thickness of the transparentinsulating film 17. If the film thickness of the transparent insulatingfilm is equal to or more than 400 nm, it is possible to realize thestable light extraction efficiency of about 54%. Thus, the filmthickness of the transparent insulating film 17 is preferably equal toor more than 400 nm.

Regarding electrode arrangement in the micro light emitting element 100g, similar to Embodiment 1 or Embodiment 2, a configuration in which thecommon N-electrode (light emitting surface-side electrode) 40 isdisposed on the light emitting surface side may be made. Similar toEmbodiment 4 or Embodiment 5, a configuration in which the metalreflective layer 20W is brought into contact with the N-side layer 11and the N-electrode 20N is disposed on the surface on the opposite sideof the light emitting surface side may be made.

As described above, similar to Embodiment 1, it is also possible toimprove the light extraction efficiency and to prevent the occurrence oflight leakage between the micro light emitting elements 100 g adjacentto each other.

Embodiment 9

(Configuration of Image Display Element 200 h)

Still another embodiment of the present invention will be describedbelow with reference to FIGS. 19 to 21. For easy description, membershaving the same functions as the members described in the aboveembodiment are denoted by the same reference signs, and repetitivedescriptions thereof will not be made. An image display element 200 h inEmbodiment 9 is different from the image display element 200 inEmbodiment 1 in that only a single electrode layer is provided inaddition to the common N-electrode 40. The image display element 200 his the same as the image display element 200 except for the above point.

FIG. 19 is a schematic sectional view of the image display element 200 haccording to Embodiment 9 of the present invention. As illustrated inFIG. 19, a micro light emitting element 100 h in the image displayelement 200 h has a structure in which the P-electrode (first metalfilm) 20P and the metal reflective layer (second metal film) 20W arejoined to each other. That is, the metal reflective layer 20W is alsoused as the P-electrode 20P. In Embodiments 1 to 5, the first metal filmand the second metal film are metal films separate from each other andare not in contact with each other. However, in this embodiment, thefirst metal film and the second metal film are joined to each other tobe continuous, and are integrally formed.

The P-electrode 20P is directly in contact with the P-side layer 13. TheP-electrode 20P covers the surface of the micro light emitting element100 h on the P-side layer 13 side, and covers the slope 16S and theN-side layer side surface 11S through the transparent insulating film17. Thus, it is possible to prevent the occurrence of light leakagebetween micro light emitting elements 100 h adjacent to each other andto reduce the occurrence of optical crosstalk. In addition, since thetransparent insulating film 17 is disposed between the P-electrode 20P,and the slope 16S and the N-side layer side surface 11S, it is possibleto realize high light extraction efficiency.

The micro light emitting element 100 h includes an insulating layer 61for preventing electrical short circuit between the P-electrode 20P andthe common N-electrode 40. In order to reduce the occurrence of opticalcrosstalk, the P-electrode 20P preferably covers the N-side layer sidesurface 11S up to the upper end of the N-side layer side surface.However, if the insulating layer 61 is not provided, a short circuitbetween the P-electrode 20P and the common N-electrode 40 occurs at theupper end portion of the micro light emitting element 100 h.

Thus, it is necessary to provide the insulating layer 61 for coveringthe upper end portion of the micro light emitting element 100 h, in thepixel region 1. In the N connection region 3, since a contact betweenthe N-electrode 20N and the common N-electrode 40 is preferable, it isnot necessary to provide the insulating layer 61. A contact portionbetween the N-electrode 20N and the common N-electrode 40 may be acurrent path in a dummy connection element 101 h in the N connectionregion 3. Similar to the micro light emitting element 100 in Embodiment1, a current may flow between the N-electrode 20N and the commonN-electrode 40 through the N-side layer 11.

(Manufacturing Flow of Micro Light Emitting Element 100 h)

FIGS. 20(a) to 20(f) are schematic sectional views illustrating themanufacturing flow of the micro light emitting element 100 h accordingto Embodiment 9 of the present invention. The manufacturing flow of themicro light emitting element 100 h is similar to the manufacturing flowof the micro light emitting element 100 in Embodiment 1 except that theP-side metal layer 10 is not deposited. Only differences between themanufacturing flow of the micro light emitting element 100 h and themanufacturing flow of the micro light emitting element 100 will bedescribed below.

In the configuration of the micro light emitting element 100 h, incomparison to the configuration of the micro light emitting element 100,the P-contact hole 19P is preferably formed as large as possible suchthat the P-side layer 13 having high sheet resistance is directly incontact with the P-electrode 20P. In the configuration of the microlight emitting element 100 h, since the P-electrode 20P and the metalreflective layer 20W are integrated, it is not necessary to performpattern processing on the metal layer 20 in the pixel region 1 and the Nconnection region 3. Since it is not necessary to deposit the P-sidemetal layer 10 and to perform pattern processing on the metal layer 20,the manufacturing flow of the micro light emitting element 100 becomessimpler than the manufacturing flow of the micro light emitting element100, and it is possible to reduce manufacturing cost.

(Manufacturing Flow of Image Display Element 200 h)

FIGS. 21(a) to 21(c) are schematic sectional views illustrating themanufacturing flow of the image display element 200 h according toEmbodiment 9 of the present invention. In descriptions of themanufacturing flow of the image display element 200 h, the growthsubstrate 9 side is set to be upper, and the driving circuit substrate50 side is set to be lower. As illustrated in FIG. 21(a), a process ofconnecting the P-electrode 20P in the micro light emitting element 100 hto the P-drive electrode 51 in the driving circuit substrate 50 with thebonding material 70 is similar to the process illustrated in FIG. 3(b).

As illustrated in FIG. 21(b), a process of removing the growth substrate9 is also similar to the process illustrated in FIG. 3(c). In themanufacturing flow of the image display element 200 h, with the processof removing the growth substrate 9, the metal layer 20 is divided foreach micro light emitting element 100 h, and the P-electrode 20P isformed. Similarly, in the N connection region 3, the N-electrode 20N isformed by the process of removing the growth substrate 9.

After the P-electrode 20P and the N-electrode 20N are formed, similar tothe processes illustrated in FIGS. 3(d) and 3(e), a space between microlight emitting elements 100 h is filled with the filling material 60 toform the common N-electrode 40. Generally, at a stage at which coatingwith the filling material 60 is performed, a resin layer remains on theupper surface of the micro light emitting element 100 h by the fillingmaterial 60. Thus, it is necessary to remove the resin layer remainingon the upper surface of the micro light emitting element 100 h. In aprocess of removing the resin layer, the resin layer between the microlight emitting elements 100 h remains, and thus it is possible to formthe insulating layer 61 between the micro light emitting elements 100 h.As described above, the material of the insulating layer 61 may be thesame as or different from the material of the filling material 60.

In a process illustrated in FIG. 20(f), after the metal layer 20 isdeposited, a process of removing the metal layer 20 at a predetermineddepth from the bottom of the isolation trench 18 may be added. Forexample, the bottom of the isolation trench 18 in the pixel region 1 isopened by the photolithographic method, and the metal layer 20 is etchedby the dry etching method or the wet etching method.

In this case, in a process illustrated in FIG. 21(b), the position ofthe upper end portion of the P-electrode 20P may be located to be lowerthan the upper surface of the N-side layer 11. As a result, theP-electrode 20P is not in contact with the common N-electrode 40, andthus it is possible to omit formation of the insulating layer 61.Compared to a case where the P-electrode 20P does not cover the entiretyof the N-side layer side surface 11S, it is possible to sufficientlyrealize an effect of significantly preventing the occurrence of lightleakage. As described above, the configuration of the image displayelement 200 h has an additional advantage in that, since the micro lightemitting element 100 h is configured by a single metal film (electrodelayer), the manufacturing flow is simplified, and the manufacturing costis reduced.

Embodiment 10

(Configuration of Image Display Element 200 i)

Still another embodiment of the present invention will be describedbelow with reference to FIG. 22. For easy description, members havingthe same functions as the members described in the above embodiment aredenoted by the same reference signs, and repetitive descriptions thereofwill not be made. An image display element 200 i in Embodiment 10 isdifferent from the image display element 200 in Embodiment 1 in that onemicro light emitting element 100 i includes a plurality of mesas 16. Theimage display element 200 i is the same as the image display element 200except for the above point.

(Manufacturing Flow of Micro Light Emitting Element 100 i)

FIGS. 22(a) to 22(f) are schematic sectional views illustrating themanufacturing flow of a micro light emitting element 100 i according toEmbodiment 10 of the present invention. In descriptions of themanufacturing flow of the image display element 200 i, the P-side layer13 side is set to be upper, and the growth substrate 9 side is set to belower. The micro light emitting element 100 i will be described withreference to FIG. 22. Here, a case where one micro light emittingelement 100 i includes two mesas will be described. However, thefollowing descriptions are similarly applied to a case where one microlight emitting element 100 i includes three mesas or more.

In addition, descriptions will be made by using a structure similar tothe structure of the micro light emitting element 100 h in Embodiment 9,as the structure of the micro light emitting element 100 i. Thestructure of the micro light emitting element 100 i may be similar tothe structure of the micro light emitting element in the embodimentsother than Embodiment 9. As illustrated in FIG. 22(b), the separationtrench 15 constituting the slope 16S is formed, and at the same time, aninternal separation trench 15 i that divides the light emission layer 12of one micro light emitting element into two pieces is formed.

The internal separation trench 15 i is formed to be smaller than theseparation trench 15. The depth of the internal separation trench 15 imay be smaller than the depth of the separation trench 15. After theseparation trench 15 and the internal separation trench 15 i are formed,as illustrated in FIG. 22(c), the isolation trench 18 is formed. Theisolation trench 18 is formed only in the bottom of the separationtrench 15, and is not formed in the bottom of the internal separationtrench 15 i. In this manner, the outer shape of the micro light emittingelement 100 i is determined by the separation trench 15 and theisolation trench 18. The internal separation trench 15 i divides thelight emission layer 12 of one micro light emitting element 100 i intotwo pieces.

After the isolation trench 18 is formed, as illustrated in FIG. 22(d),the transparent insulating film 17 is deposited and then the P-contactholes 19P are formed as illustrated in FIG. 22(e). Here, the P-contacthole 19P is formed for each mesa 16. Processes subsequent to the processof forming the P-contact hole 19P, including the manufacturing flow ofthe image display element 200 i, are the same as those in themanufacturing flow of the image display element 200 h in Embodiment 9.In the N connection region 3, it is not necessary that a dummyconnection element 101 i in the image display element 200 i has aconfiguration of including a plurality of mesas 16. The dummy connectionelement 101 i may have the same configuration as that of the dummyconnection element 101 h in Embodiment 9.

The micro light emitting element 100 i including the plurality of mesas16 is useful in the following cases of (1) and (2). (1) Used inredundant relief. P-electrodes 20P which are independent from each otherare arranged in each mesa 16, and drives independently for each mesa 16.A current does not flow in one of two mesas 16, which does not shownormal light emission. Since the current flows only in one normal mesa,it is possible to significantly reduce the defect rate of the microlight emitting element 100 i.

(2) Increasing the light emission efficiency of the relatively largemicro light emitting element 100 i. As illustrated in FIG. 6(b), as thesize of the slope 16S increases, the light extraction efficiency isimproved. Thus, a large slope is required for the large micro lightemitting element 100 i. However, it is difficult to form the large slopein terms of a manufacturing technology. Thus, in accordance with thesize of a slope which can be produced, the plurality of mesas 16 isformed to an extent that the light extraction efficiency is improved tothe maximum, the light emission layer 12 of the micro light emittingelement is divided by the plurality of mesas 16, and the lightextraction efficiency in the entirety of the micro light emittingelement is improved.

As described above, similar to Embodiment 1, it is also possible toimprove the light extraction efficiency and to prevent the occurrence oflight leakage between the micro light emitting elements 100 i adjacentto each other.

Embodiment 11

(Configuration of Image Display Element 200 j)

Still another embodiment of the present invention will be describedbelow with reference to FIG. 23. For easy description, members havingthe same functions as the members described in the above embodiment aredenoted by the same reference signs, and repetitive descriptions thereofwill not be made. An image display element 200 j in Embodiment 11 isdifferent from those in the above embodiments in that the transparentinsulating film (first transparent insulating film) 17 that covers theslope 16S and the second transparent insulating film 28 that covers theN-side layer side surface 11S are separate members. The configuration ofthe image display element 200 j is similar to the configuration of theimage display element 200 c in that the metal reflective layer 20W andthe N-side layer side surface 11S are connected to each other at aportion of the N-side layer side surface 11S of the micro light emittingelement 100 c in Embodiment 4, and the metal reflective layer 20W isalso used as the N-electrode 20N.

The configuration of the image display element 200 j is similar to theimage display element 200 e in Embodiment 6 in that the P-sidetransparent insulation film (third transparent insulating film) 25 isdisposed between the P-side layer 13 and the P-side metal layer 10 e inEmbodiment 6. Thus, the image display element 200 j has an additionaladvantage in that it is not necessary to form the common N-electrode 40after the micro light emitting element and the driving circuit substrateare stuck to each other, and the growth substrate 9 is removed, and hasan additional advantage in that the light extraction efficiency isfurther improved by the P-side transparent insulation film 25.

(Manufacturing Flow of Micro Light Emitting Element 100 j)

FIGS. 23(a) to 23(j) are schematic sectional views illustrating themanufacturing flow of a micro light emitting element 100 j according toEmbodiment 11 of the present invention. The micro light emitting element100 j is included in the image display element 200 j. In descriptions ofthe manufacturing flow of the micro light emitting element 100 j, theP-side layer 13 side is set to be upper, and a growth substrate 9 sideis set to be lower. As illustrated in FIG. 23(a), the compoundsemiconductor 14 is stacked by sequentially stacking the N-side layer11, the light emission layer 12, and the P-side layer 13 on the growthsubstrate 9. The P-side metal layer as in Embodiment 1 is not depositedat this stage.

After the compound semiconductor 14 is stacked, as illustrated in FIG.23(b), portions of the P-side layer 13, the light emission layer 12, andthe N-side layer 11 are etched to form the separation trench 15. At thistime, a portion including the light emission layer 12 serves as a mesa16. The slope 16S being the side surface of the mesa 16 is inclined atthe inclined angle θe, similar to other embodiments.

After the separation trench 15 is formed, as illustrated in FIG. 23(c),the transparent insulating film 17 is deposited to cover the exposedportions of the N-side layer 11, the light emission layer 12, and theP-side layer 13. Then, similar to Embodiment 6, the P-side metal layercontact hole 26 is formed at a portion of-the transparent insulatingfilm 17 deposited on the mesa 16 and then a P-side metal layer 10 j isdeposited. As a result, a state as illustrated in FIG. 23(d) occurs. Thetransparent insulating film 17 of the micro light emitting element 100 jhas a function as the transparent insulating film (first transparentinsulating film) that covers the slope 16S and as the P-side transparentinsulation film (third transparent insulating film) 25 in Embodiment 6.

After the P-side metal layer 10 j is deposited, as illustrated in FIG.23(e), the P-side metal layer 10 j is processed to a P-side metal layerpattern 10P by the photolithographic method and the dry etching method.The P-side metal layer pattern 10P covers at least the P-side layer 13deposited on the mesa 16 and covers at least a portion of the slope 16S.

After the P-side metal layer 10 j is processed to the P-side metal layerpattern 10P, as illustrated in FIG. 23(f), the isolation trench 18 isformed in the bottom of the separation trench 15. Processing of theP-side metal layer pattern 10P may be performed simultaneously withformation of the isolation trench 18. The N-side layer side surface 11Sbeing the side surface of the isolation trench 18 is inclined at theinclined angle θb, similar to other embodiments.

After the isolation trench 18 is formed, as illustrated in FIG. 23(g),the second transparent insulating film 28 is deposited to cover exposedportions of the transparent insulating film 17, the P-side metal layerpattern 10P, the N-side layer side surface 11S, and the growth substrate9. The material similar to that for the transparent insulating film 17can be applied to the second transparent insulating film 28. After thesecond transparent insulating film 28 is deposited, as illustrated inFIG. 23(h), similar to FIG. 12(b) in Embodiment 4, the P-contact hole19P and the bottom opening 19BN are formed in the second transparentinsulating film 28.

Then, as illustrated in FIG. 23(i), the metal layer 20 is deposited tocover exposed portions of the N-side layer 11, the P-side metal layerpattern 10P, the transparent insulating film 17, and the secondtransparent insulating film 28. Further, as illustrated in FIG. 23(j),the metal layer 20 is processed to be the P-electrode 20P and the metalreflective layer 20W which is also used as the N-electrode 20N. Theprocesses are similar to the processes illustrated in FIGS. 12(c) and12(d). Similar to the processes illustrated in FIGS. 12(e) and 12(f) inEmbodiment 4, in the manufacturing flow of the image display element 200j, the micro light emitting element 100 j is connected to the drivingcircuit substrate 50 c by the bonding material 70, and the growthsubstrate 9 is removed.

In the configuration of the image display element 200 j, most of theN-side layer side surface 11S is covered by the second transparentinsulating film 28, and the metal reflective layer 20W covers the outerside of the second transparent insulating film 28. A portion of theupper portion of the slope 16S is covered by the transparent insulatingfilm 17 and the P-side metal layer pattern 10P. A portion of the lowerportion of the slope 16S is covered by the transparent insulating film17 and the second transparent insulating film 28. The outer side of thesecond transparent insulating film 28 is covered by the metal reflectivelayer 20W.

A portion of the center portion of the slope 16S is covered by thetransparent insulating film 17 and the P-side metal layer pattern 10P.The outer side of the P-side metal layer pattern 10P is covered by thesecond transparent insulating film 28 and the metal reflective layer20W. The P-side metal layer pattern 10P and the metal reflective layer20W are disposed to overlap each other, and thus the occurrence of lightleakage from the micro light emitting element 100 j to the outside isprevented.

In the configuration of the image display element 200 j, most of theN-side layer side surface 11S, the slope 16S, and most of the P-sidelayer 13 can be covered by the transparent insulating film 17 and thesecond transparent insulating film 28, and the metal reflective layer20W as a metal film having high reflectivity can be disposed on theoutside of the second transparent insulating film 28. Thus, it ispossible to realize very high light extraction efficiency while theoccurrence of light leakage is prevented. In the image display element200 j, as illustrated in FIG. 23(j), the second transparent insulatingfilm 28 is disposed between the N-side layer side surface 11S and themetal reflective layer 20W.

Embodiment 12

(Configuration of Image Display Element 200 k)

Still another embodiment of the present invention will be describedbelow with reference to FIG. 24. For easy description, members havingthe same functions as the members described in the above embodiment aredenoted by the same reference signs, and repetitive descriptions thereofwill not be made. An image display element 200 k in Embodiment 12 isdifferent from the image display element 200 j in Embodiment 11 in thatthe configuration of the transparent insulating film (first transparentinsulating film) 17 that covers the slope 16S, and the P-sidetransparent insulation film (third transparent insulating film) 25 aredifferent. In the image display element 200 k, the connection method ofthe metal electrode to the N-side layer 11 is different from that in theimage display element 200 j, but it is possible to realize an effectsimilar to that in the image display element 200 j.

(Manufacturing Flow of Micro Light Emitting Element 100 k)

FIGS. 24(a) to 24(i) are schematic sectional views illustrating themanufacturing flow of a micro light emitting element 100 k according toEmbodiment 12 of the present invention. The micro light emitting element100 k is included in the image display element 200 k. A state afterprocesses similar to the processes illustrated in FIGS. 23(a) to 23(c)are performed is a state illustrated in FIG. 24(a).

A transparent insulating film formed at a stage of the processillustrated in FIG. 24(a) is set to a transparent insulating film 17A.Then, as illustrated in FIG. 24(b), the isolation trench 18 is formed inthe bottom of the separation trench 15. The N-side layer side surface11S being the side surface of the isolation trench 18 is inclined at theinclined angle θb, similar to other embodiments. Preferably, a flatportion for forming the N-contact hole 19N remains in the bottom of theseparation trench 15 even after the isolation trench 18 is formed.

After the isolation trench 18 is formed, as illustrated in FIG. 24(c), atransparent insulating film 17B is deposited to cover exposed portionsof the N-side layer side surface 11S, the transparent insulating film17A, and the growth substrate 9. Further, as illustrated in FIG. 24(d),the N-contact hole 19N is formed at portions of the transparentinsulating films 17A and 17B, which are deposited on the flat portion ofthe separation trench 15.

After the N-contact hole 19N is formed, as illustrated in FIG. 24(e),the metal layer 20 is deposited to cover exposed portions of the N-sidelayer 11 and the transparent insulating films 17A and 17B. After themetal layer 20 is deposited, as illustrated in FIG. 24(f), the metallayer 20 is processed and patterned to the metal reflective layer 20W bythe photolithographic method and the dry etching method. The metalreflective layer 20W covers the N-side layer side surface 11S and theslope 16S. The metal reflective layer 20W is electrically connected tothe N-side layer 11 in the N-contact hole 19N. The metal reflectivelayer 20W may cover the isolation trench 18 and the separation trench15.

After the metal layer 20 is patterned and processed, as illustrated inFIG. 24(g), a transparent insulating film 17C is deposited to coverexposed portions of the transparent insulating film 17B and the metalreflective layer 20W, and the surface of the transparent insulating film17C is flattened by the CMP method. After the surface of the transparentinsulating film 17C is flattened, as illustrated in FIG. 24(h), theP-side metal layer contact hole 26 is formed by removing the transparentinsulating films 17A, 17B, and 17C, so as to expose the P-side layer 13.

An N-side metal layer contact hole 29 is formed by removing thetransparent insulating film 17C, so as to expose the metal reflectivelayer 20W. A P-side metal layer 10 k is deposited to cover exposedportions of the P-side layer 13, the transparent insulating film 17C,and the metal reflective layer 20W. A process of depositing the P-sidemetal layer 10 k is performed in a manner similar to the process ofdepositing the P-side metal layer 10 e in the image display element 200e in Embodiment 6. After the P-side metal layer 10 k is deposited, asillustrated in FIG. 24(i), the P-electrode 20P and the N-electrode 20Nare formed by performing pattern processing on the P-side metal layer 10k.

In the configuration of the image display element 200 k, as illustratedin FIG. 24(i), the transparent insulating film (second transparentinsulating film) 17B covers the N-side layer side surface 11S, and astacked film (first transparent insulating film) of the transparentinsulating film 17A and the transparent insulating film 17B covers theslope 16S. In addition, a stacked film of the transparent insulatingfilm 17A, the transparent insulating film 17B, and the transparentinsulating film 17C serves as the P-side transparent insulation film(third transparent insulating film). In plan view from a side oppositeto the light emitting surface side, the metal reflective layer 20W andthe P-electrode 20P are disposed to overlap each other.

The damascene method can be employed for a manufacturing flow of themetal reflective layer 20W in the image display element 200 k. That is,after the metal layer 20 is buried in the separation trench 15 and theisolation trench 18, the surface of the metal layer 20 is flattened bythe CMP method, and the transparent insulating film 17B on the mesa 16is exposed. Thereby, the metal reflective layer 20W can be formed. Inthis case, it is not necessary to flatten the surface of the transparentinsulating film 17C by the CMP method. There is an advantage in that adifference between the depth of the N-side metal layer contact hole 29and the depth of the P-side metal layer contact hole 26 is small, and itis easy to simultaneously form the N-side metal layer contact hole 29and the P-side metal layer contact hole 26.

As described above, similar to Embodiment 1, it is also possible toimprove the light extraction efficiency and to prevent the occurrence oflight leakage between the micro light emitting elements 100 k adjacentto each other.

CONCLUSION

According to Aspect 1 of the present invention, a micro light emittingelement includes a compound semiconductor in which a first conductivelayer, a light emission layer, and a second conductive layer having aconductivity type opposite to a conductivity type of the firstconductive layer are stacked in order from a light emitting surfaceside. A first metal film electrically connected to the second conductivelayer is disposed on a surface on an opposite side of the light emittingsurface side. The first metal film covers the second conductive layer. Aslope is formed around the light emission layer. A first inclined angleof a first conductive layer side surface from the slope to the lightemitting surface is larger than a second inclined angle of the slope.The slope and the first conductive layer side surface are coveredtogether by a second metal film. A first transparent insulating film isdisposed between the slope and the second metal film.

According to Aspect 2 of the present invention, in Aspect 1, a secondtransparent insulating film may be disposed between the first conductivelayer side surface and the second metal film.

According to Aspect 3 of the present invention, in Aspect 2, the secondtransparent insulating film may be obtained by the first transparentinsulating film extending between the first conductive layer sidesurface and the second metal film.

According to Aspect 4 of the present invention, a micro light emittingelement includes a compound semiconductor in which a first conductivelayer, a light emission layer, and a second conductive layer having aconductivity type opposite to a conductivity type of the firstconductive layer are stacked in order from a light emitting surfaceside. A first metal film electrically connected to the second conductivelayer is disposed on a surface on an opposite side of the light emittingsurface side. The first metal film covers the second conductive layer. Aslope is formed around the light emission layer. The slope extends tothe light emitting surface and is covered by a second metal film. Afirst transparent insulating film is disposed between the slope and thesecond metal film.

According to Aspect 5 of the present invention, in Aspect 1, a thirdtransparent insulating film may be disposed between the secondconductive layer and the first metal film.

According to Aspect 6 of the present invention, in Aspect 1, in planview from an opposite side of the light emitting surface side, thesecond metal film may be disposed to overlap the first metal film.

According to Aspect 7 of the present invention, in Aspect 1, the filmthickness of the transparent insulating film may be equal to or morethan 75 nm.

According to Aspect 8 of the present invention, in Aspect 7, the filmthickness of the transparent insulating film may be equal to or morethan 400 nm.

According to Aspect 9 of the present invention, in Aspect 1, the secondinclined angle may be equal to or less than 60° .

According to Aspect 10 of the present invention, in Aspect 9, the secondinclined angle may be equal to or less than 50° .

According to Aspect 11 of the present invention, in Aspect 1, the firstmetal film may include a layer containing silver or aluminum as a maincomponent, on the compound semiconductor side.

According to Aspect 12 of the present invention, in Aspect 1, the secondmetal film may include a layer containing silver or aluminum as a maincomponent, on the compound semiconductor side.

According to Aspect 13 of the present invention, in Aspect 1, thetransparent insulating film may be a SiO₂ film.

According to Aspect 14 of the present invention, in Aspect 1, the firstinclined angle may be less than 90° .

According to Aspect 15 of the present invention, in Aspect 1, the secondmetal film may be electrically connected to the first conductive layer.

According to Aspect 16 of the present invention, in Aspect 15, the microlight emitting element may further include a second electrodeelectrically connected to the second metal film, on an opposite side ofthe light emitting surface side.

According to Aspect 17 of the present invention, in Aspect 1, the microlight emitting element may further include a light emitting surface-sideelectrode configured from a transparent conductive film electricallyconnected to the first conductive layer, on a surface of the firstconductive layer on the light emitting surface side.

According to Aspect 18 of the present invention, an image displayelement may have a pixel region in which micro light emitting elementsin any of Aspects 1 to 17 are arranged on a driving circuit substrate ina two-dimensional array shape. A surface of the micro light emittingelement on an opposite side of the light emitting surface side may facea surface of the driving circuit substrate. First driving electrodes forsupplying a current to the micro light emitting elements may be arrangedin a two-dimensional array shape on a surface of the driving circuitsubstrate in the pixel region. A first electrode and the first drivingelectrode may be connected in a one-to-one relation, and the firstelectrode may be disposed on a surface on an opposite side of the lightemitting surface side and be electrically connected to the first metalfilm.

According to Aspect 19 of the present invention, an image displayelement may have a pixel region in which micro light emitting elementsin Aspect 17 are arranged on a driving circuit substrate in atwo-dimensional array shape. A surface of the micro light emittingelement on an opposite side of the light emitting surface side may facea surface of the driving circuit substrate. First driving electrodes forsupplying a current to the micro light emitting elements may be arrangedin a two-dimensional array shape on a surface of the driving circuitsubstrate in the pixel region. A first electrode and the first drivingelectrode may be connected in a one-to-one relation, and the firstelectrode may be disposed on a surface on an opposite side of the lightemitting surface side and be electrically connected to the first metalfilm. A second driving electrode may be disposed on a surface of thedriving circuit substrate on an outside of the pixel region. The seconddriving electrode may be electrically connected to the light emittingsurface-side electrode.

According to Aspect 20 of the present invention, an image displayelement may have a pixel region in which micro light emitting elementsin Aspect 16 are arranged on a driving circuit substrate in atwo-dimensional array shape. A surface of the micro light emittingelement on an opposite side of the light emitting surface side may facea surface of the driving circuit substrate. First driving electrodes andsecond driving electrodes for supplying a current to the micro lightemitting elements may be arranged in a two-dimensional array shape on asurface of the driving circuit substrate in the pixel region. A firstelectrode and the first driving electrode may be connected in aone-to-one relation, and the first electrode may be disposed on asurface on an opposite side of the light emitting surface side and beelectrically connected to the first metal film. The second electrode andthe second driving electrode may be connected to each other.

The present invention is not limited to the above-described embodiments,and various modifications can be made within the scope of the claims.Embodiments obtained by appropriately combining the technical meansdisclosed in the different embodiments are included in the technicalscope of the present invention. Further, a new technical feature can beformed by combining the technical means disclosed in the embodiments.

REFERENCE SIGNS LIST

-   -   100, 100 a, 100 b, 100 c, 100 d, 100 g, 100 h, 100 i, 100 j, 100        k MICRO LIGHT EMITTING ELEMENT    -   1 PIXEL REGION    -   10, 10 e, 10 f, 10 j, 10 k P-SIDE METAL LAYER (FIRST METAL FILM)    -   11 N-SIDE LAYER (FIRST CONDUCTIVE LAYER)    -   11S N-SIDE LAYER SIDE SURFACE (FIRST CONDUCTIVE LAYER SIDE        SURFACE)    -   12 LIGHT EMISSION LAYER    -   13 P-SIDE LAYER (SECOND CONDUCTIVE LAYER)    -   14 COMPOUND SEMICONDUCTOR    -   16S SLOPE    -   17 TRANSPARENT INSULATING FILM    -   20N N-ELECTRODE (SECOND ELECTRODE)    -   20P P-ELECTRODE (FIRST ELECTRODE)    -   20W METAL REFLECTIVE LAYER    -   25, 25 f P-SIDE TRANSPARENT INSULATION FILM    -   28 SECOND TRANSPARENT INSULATING FILM    -   40 COMMON N-ELECTRODE (LIGHT EMITTING SURFACE-SIDE ELECTRODE)    -   50, 50 c, 50 d DRIVING CIRCUIT SUBSTRATE    -   51 P-DRIVE ELECTRODE (FIRST DRIVING ELECTRODE)    -   52 N-DRIVE ELECTRODE (SECOND DRIVING ELECTRODE)    -   200, 200 a, 200 b, 200 c, 200 d, 200 e, 200 f, 200 g, 200 h, 200        i, 200 j, 200 k IMAGE DISPLAY ELEMENT    -   θb INCLINED ANGLE (FIRST INCLINED ANGLE)    -   θe INCLINED ANGLE (SECOND INCLINED ANGLE)

The invention claimed is:
 1. An image display element having a pixelregion in which micro light emitting elements are arranged on a drivingcircuit substrate in a two-dimensional array shape, and an upper surfaceof each of the micro light emitting elements is a light emittingsurface, and a lower surface of each of the micro light emittingelements is a surface on an opposite side of the upper surface of eachof the micro light emitting elements, and the lower surface of each ofthe micro light emitting elements faces a surface of the driving circuitsubstrate, wherein the micro light emitting element comprising: acompound semiconductor in which a first conductive layer, a lightemission layer, and a second conductive layer having a conductivity typeopposite to a conductivity type of the first conductive layer arestacked in order from an upper side to a lower side; wherein thecompound semiconductor has a slope formed around the light emissionlayer and having a second inclined angle and has a first conductivelayer side surface extending from the slope to an upper surface of thecompound semiconductor and having a first inclined angle; and whereinthe first inclined angle is larger than the second inclined angle, andthe first inclined angle is less than 90° ; and a second metal filmwhich covers both the slope and the first conductive layer side surface;and a first transparent insulating film which is disposed between theslope and the second metal film, wherein the upper surface of thecompound semiconductor and an upper surface of the second metal film arein a same plane.
 2. The image display element according to claim 1,wherein a second transparent insulating film is disposed between thefirst conductive layer side surface and the second metal film of themicro light emitting element.
 3. The image display element according toclaim 2, wherein the second transparent insulating film is an extensionof the first transparent insulating film to the first conductive layerside surface.
 4. The image display element according to claim 2, whereinthe second metal film is disposed on the lower surface of each of themicro light emitting elements.
 5. The image display element according toclaim 4, wherein the second metal film is electrically connected to thesecond conductive layer.
 6. The image display element according to claim4, wherein, in plan view from a side of the lower surface of each of themicro light emitting elements, the second metal film covers the compoundsemiconductor entirely.
 7. The image display element according to claim5, wherein the second metal film comprises a first electrode of themicro light emitting element.
 8. The image display element according toclaim 1, wherein a first metal film is disposed on a lower surface ofthe compound semiconductor and the first metal film is spaced apart fromthe second metal film, and the first metal film covers the secondconductive layer, wherein the first metal film is electrically connectedto the second conductive layer.
 9. The image display element accordingto claim 8, wherein the second metal film is electrically connected tothe first conductive layer.
 10. The image display element according toclaim 8, wherein a third transparent insulating film is disposed betweenthe second conductive layer and the first metal film.
 11. The imagedisplay element according to claim 8, wherein, in plan view from a sideof the lower surface of each of the micro light emitting elements, thesecond metal film is disposed to overlap the first metal film.
 12. Theimage display element according to claim 9, wherein the second metalfilm comprises a second electrode of the micro light emitting element.13. The image display element according to claim 1, wherein a filmthickness of the first transparent insulating film is equal to or morethan 75 nm.
 14. The image display element according to claim 13, whereinthe film thickness of the first transparent insulating film is equal toor more than 400 nm.